OK well, then, with this info, I suggest and take this with no ill thoughts meant
MAYBE you should take to a good foot DR, as you might have some blood flow issue's

as 3 hours sitting, pending HOW cold it is isn;t very long
As honestly everyone has different tolerances to cold, and honestly;y blood flow is a BIG part of keeping digits warm(toes and fingers), as there the farthest from the heart!
also, pending any med's you might be on could be causing you some issue's too!

NOW< again, a short walk in heavy insulated boots again can MAKE a foot sweat, all the more so when you go from hot/warm house into a COLD air
ever see condensation build on a window when cold air meets warm air?
there simply is moisture in the air,
NOW< again as for boots, Yes more insulation SHOULD help prevent cold from seeping into boots before hitting toes
with this mind set, again, having the most insulation you can get and THEN adding Boot blankets can only help you more so??

But I hate walking in big heavy boots, I again prefer lighter GOOD fitting boots I find comfortable, and I have many times in extreme cold weather, taken my boots off and just used a few heat packets and boot blankets on long all day sits!

something else to think about, is what do you KEEP your feet on when on stand?
the ground, in the air ina stand or??

adding a layer between you and the frozen ground can also help, like adding some thick carpet between your feet and ground or stand

you also might benefit from something like a body suit, or heck even bringing a good heavy insulated blanket to wrap your feet in(if you san safely do so!)
as it sort of sounds to me like your hunting private lands close to home
if this is the case, you can also LEAVE many things at stand site in waterproof totes or?? saving carrying in ever day

I used to do this on many hunts as well FAR in, , only I used water proof dry bags and would some what bury them to hide my things, this was I could walk in and out not having to carry much of anything!

but I am a firm believer in the fact walking generates body temp rise, your working muscles and that makes heat, as you sit still and don;'t move , all that heat dissipates, and many times leaves moisture behind, and then that makes you COLD a LOT faster, this is why I always wait about 30+ minutes at a stand to cool down, before adding the new DRY layers from socks to ??
same with letting heat OUT of boots and things

a TON of folks Love the old military Micky mouse boots for extreme cold weather, there proven to work
but back to that EVERYONE has different feet shapes and needs for them, I have Never found Micky mouse boots to be comfortable or even close tom fitting my feet!

so, this is why IMO, its very hard to ever recommend a BOOT model , for anyone else! what fits me perfectly and keeps Y feet warm, just might not fit your feet!
ever try a few pairs of different OEM boots on all CLAIMING to be the same size and see the difference in how they all fit>
same deal when recommend a boot period IMO!

This said, me I know I am more cold hearty than most, I was snowmobiling 2 yrs ago in minus 20 air temps*(not counting wind chill riding 70-80 mph) wearing 400 gram insulated boots, and mid weight gloves and jacket!, heck at times I was sweating!(working hard ruiding builds a sweat for me)
but buddies with me were freezing wearing many heavier layers than me!
sop again, we all don't handle cold the same

but my thoughts on HOW to stay warm still work the same
its starting off dry, adding good layers of gear that breath and are known to HOLD in warmth!

many guys I know (even me) have found some of them reflective type gear to work well, they CLAIM they reflect body heat back at you, winch is OK for sitting, but I melt in it walking!(like stuff made by Arctic Shield, I have a bunch of there gear, parka, jacket, pants, boot blanket and hand muffs and maybe more I forget, I have a LOT of gear HAHA)

but IMO again, boot blankets over ANY good boot will help a bunch, or JUST boot blankets and good socks and some heat packets in there
since you KNOW your toes get cold first
you can also, try this, a good base layer sock, a heavy weight sock, add a heat pack to toes, then a another heavy weight sock, and in boot blankets
I think doing this will add a lot of time to your hunts before your toes get cold, just watch out, some heat packs can BURN your toes, you need a layer between them and toes!, and they NEED to be close to toes to work, just not TOO close

a Crazy old guy I know does this but he adds aluminum foil wraps his feet in it after the second pair of socks goes on, (heat pack added too), and says that traps ALL heat inside, but seems like work to me and well NO breathing of toes, might come out at end of day a size smaller LOL

but those are some suggestions from me on this, I know I have a LOT of time spent in extreme cold, so much to the point, I think its ruined me for warm weather
as anything above say 70 I find very uncomfortable any more, opposite issue than you maybe, only, I don;t know what else to take off at times to try and help ,without getting rather naked HAHA!
cold, I can always ADD layers, but heat, just cannot shed enough to find it comfortable, I live in AC in warm weather!