I.S. staying warm on stand is one of THE toughest things going for clothing manufacturers. Keeping a man warm while trudging up a mountain after elk, wading through brush after birds or while seated in a heated blind waiting on ducks is childsplay. For the stand hunter though its is necessary to insulate what precious heat is there because obviously not much is being generated. You want to trap and utilize what you worked up while walking in too the stand but you don't want to get wet from perspiration in the process!
The first and foremost crucial element actually doesn't begin with the outermost layer, it begins with what is in contact with your skin. ABSOLUTELY UNDER NO CIRCUMSTANCES do you want cotton on your skin if you are trying to stay warm while being stationary. Cotton absorbs moisture and doesn't wick it away from your skin. If you remain dry you would be surprised how comfortable you can be in cold climates. So you want your innersocks and insulated underwear made of synthetic materials like Thermax etc. If you aren't allergic too it (which I am if it's in direct contact) wool is natures GREATEST material.
When the mercury is really cold (below 25 for this TN boy, I spend many days in teens and single digit temps while on stand) I will have on a union suit which is a blend of thermax, wool and cotton. These suits are to warm for moderate condtions but work GREAT when really cold as they fully insulate the body while still keeing it dry. ALOT of bodyheat is lost around the waist while seated, even if you have a good outer suit on. A union suit prevents that loss. I also have converted MANY of my customers too a two sock setup. First a thin "innersock" also made of some type of fast wicking, non-absorbing synthetic. Followed over by a heavy insulated sock of wool or sometype of wool, synthetic blend. Again the main concern is keeping your feet dry, especially while wearing rubber boots as they don't breath so it's then doubly important to keep the moisture off your foot. (And also using a boot dryer at night, drying out a boot not only adds to it's lifespan by years, but also keeps your foot warmer during use because the lining can then absorb your foots moisture instead of being cold with the previous days use!)
With the baselayer taken care of you are much less restricted too what you can wear for your clothes themselves. A good flannel shirt, while not perfect, IS comfortable and works great as it is not full of moisture like it would be were it directly on your skin. The other various shirts out there of synthetic types are great as well. Something in a medium pile is really all you need. My largest collection of coldweather shirts is "chamois" type which simply is heavyweight, lofted cotton. Color also obviously doesn't matter as it is going to be under your outer suit, thats why I will often times be seen in insulated bluejeans and a favorite heavyweight flannel shirt. Pantwise, like I said the insulated bluejeans work GREAT as well. Wrangler also makes some heavily insulated jeans that are camo and alot of times when it is not quite warm enough for heavy outerwear (when temps are in the upper 30s-40s and might climb higher as the day goes on) I will just wear a pair of brown or camo insulated Wrangler jeans and they suffice for my lower body. Plain ol blue jeans are ok for a lastresort, but again make sure that cotton isn't directly on your skin.
Outerwear is more available now than every before. Up until the last few years your choices were simple and basic. You could spend the big bucks and buy a full Columbia or Browning parka and bibs setup or you could stick with cheap and get a Dickies or Walls insulated coverall at Walmart. Now with cheap foreign imports ANYONE can have a first class, waterproof, multi-function parka and matching bibs for less than $200-$300! (I remember when Brownings Quad Parkas were nearly $500 just by them selves). In some cases, like with the company "Core Products Inc" and Whitewater, many of their clothing items come from the EXACT same assembly lines in China and Vietnam as Browning and Columbia. I will admit I have one of those high dollar Browning quads and it's been around for 10 years and likely will for decades more. BUT I also have other pieces from Columbia, Core, Whitewater, 10x, Dickies, Avery etc and they all work great as well.
You mentioned your feet, hands and head. And the most heat is lost through those parts of the body. Bootwise it depends on what you like, I prefer all rubber boots and have 3 pairs of the Lacrosse "Burly" kneeboots of various weight insulation from non-insulated too 1200grams of Thinsulate. I also have MANY other pairs of boots of various makes and styles (my wife kids me about having as many pairs of hunting boots as she does high heels!) but primarily the Lacrosse get the nod. Regardless of what boot you have it all goes back too what I was saying about the sock system you have. A dry foot will be MUCH warmer and more comfortable than a wet or clamy one. (And like I said, I cannot over emphasize the difference drying your boots at night will make!) Have you tried the various "boot insulators" on the market? Boot Blankets are the biggest sellers on the market but I consider than too big and bulky to haul in and out of the woods and they are noisy as well, BUT they do work if you have taken the other precautions I first gave. I prefer the Boot Insulators from Artic Shield. They are 1/3 less thick as the Blankets, they roll up easily into a backpack or legpocket and are made of Artic-Shields material which is much more insulation intense than simply pilin on the nylon and a little Thinsulate like most "Blanket" varieties.
You also mentioned your legs, they primarily are probably getting cold because your feet are getting cold first and you likewise don't have enough insulation on the lowerhalf of your body. Again, a quality bib over the proper insulation with the first two layers will help, BUT if you still find yourself getting cold there are other alternatives. And I find my mind blank right now, but the various "standblankets" on the market are literally the cats arse for guys like yourself. They basically are waterproof and insulated sleeping bags that are cut in half and worn over the lower 1/2 of your body while stationary. I have one but can't for the life of me remember who makes it (I want to say it's a Core product but don't quote me on that). Anyway they roll up like a sleeping bag (except about half the size, diameter wise) and are REALLY good for staying warm. They cut ALL the wind, moisture and cold off your legs and feet so they really allow your insulated clothing to work. I think one of those would be THE elimination too your problems.
Hands wise, again I recommend wool over the notoriously crappy "Gates" goretex skigloves that are died camo and sold as hunting gloves. There are several now on the market, but I have used them for years and they are a raggwool outter glove with a thinsulate lining inside of them with leather or rubberdot palms for grabbing. If it's REALLY cold they even make them with a pullover "mitten" cup that cuts the exterior conditions off your fingers. But I prefer to have my fingers free while hunting. They obviously aren't waterproof but when used in 25 degrees or colder temps any precipitation is gonna be frozen anyway. For cold rainy days (45 and colder) I recommend a good pair of neoprene gloves. They are much thinner and warmer than the Gates type and you can feel your equipment with them much better as well. Avery makes a great pair, I actually prefer the gaunlet style (elbow length) as they keep the cuffs and arms of your clothing from being bulky (for bowhunting for instance) and also eliminate heat loss and water away from your wrist area. BTW ALL the gloves I also mention and use I recommend getting the extended cuff models. They keep shiny watches out of harms way and also insulate that much better. And ALOT of cold hand problems extend from the fact that you lose alot of heat through your wrists (same with the neck/head and foot/ankle areas) because the blood vessels are so close too the surface. The thickest, warmest gloves are useless if they aren't long enough to cover properly too at least the lower forearm region!
Hatwise, the head is THE body's thermostat and venting system. A properly contained noggin will actually allow you to use less insulated clothing. Wool again is the best with synthetics taking a close 2nd. Obviously there is TONS of moisture disappated through your head so you gotta be double cautious with wicking that away from your scalp. A scarf or neck gaitor also makes a BIG difference. Alot of heat is lost through the back of your neck and the tops of your shoulder. A trick I use and recommend is taking a simple disposable handwarmer and placing it on the back of your neck under a collar or neck gaitor. It keeps the blood going too your brain warm, I guess you can say you are tricking your brain into believing the body is warmer than it is. That trick REALLY does work, try it. It is simple and cheap.
You might also try some of the various facemasks. I have several of the wool/cotton mixture toboggans with the fleece face in them. I LOVE em. The face looses alot of heat as well. You might also check into a face/chin mask called the Heat Exchanger. It actually has copper wiring enclosed in synthetic material that you breath through. Using the warm breath you exhale that copper is heated and very much like a radiator you are breathing through, you then inhale warmed air through that "radiator". It sounds crazy but actually works WONDERS. The lungs and the body itself work amazingly better while breathing warmer air. You lungs don't have to warm all that cold air you inhaled so the blood stays warmer and does a better job heating the rest of your body.
Sorry for going so long and I know this was alot but hopefully it can help you understand that there IS alot out there to help hunters remain comfortable while on stand!
RA
ps
With all the above clothing you will find yourself "over-insulated" for the walk into your stand. If you put it all on you will be a sweaty, wet, overheated mass of tissue that will chill quickly once on stand. So I came up with a solution too that very problem a couple of years ago. I bought a square bottom decoy bag (Avery) and use it to haul all that insulated clothing in. It is about 3-4' deep so you carry ALOT. I load the heaviest stuff in it first (typically my backpack) and work up too the lightest. That way it sits properly on your back and doesn't move around. In the early morning while still dark I sometimes even put my rifle in it, butt end down. The top is closable with two drawstrings with quicklock clips. That leaves your hands free and with all the load on your shoulders and back you would be surprised how comfortable it is, vs either wearing all that crap in or carrying it in your arms. Even in the coldest days I usually wear nothing but my insulated underwear and regular clothes while walking in. That way I stay cool and don't get sweaty (which means scent too the deer) and really comfortable. Once at my standsite I put the stuff on and climb up in the stand. The heat generated from climbing up in the stand is sufficient to heat the innermost of the insulated outerwear and I leave the bag crumpled up below the tree, maybe under some leaves.