RE: long underwear
Think in terms of 2 sets of long underwear. I have a set I wear against my skin to wick away moisture and provide extra insulation. I usually use polypro, but have dicovered Underarmour. Warmest and driest stuff you can wear. Then, over that I have a layer of heavy wool underwear. Fleece would be a good substitute. I have hunted in weather down to 0 F and been comfortable. Also think about wearing bibs or pants with suspenders. Wearing a belt really cuts into your insulation. Bibs or suspenders allow your upper and lower body to exchange heat.