I ice fish in 800g Danners, they will go down to about -10 for a couple hours easy. Honestly your feet won't go over 98.6, but they will be sweating and with all that insulation, Goretex or not, getting rid of the moisture will be a problem. The worse problem as I see it is the physical bulk you are carrying around, that will be what you are going to learn to hate.
I understand that a body gets used to a climate and adapts. I would look into about 200g and wear some Merino wool socks if it gets down under 40 degrees. This would be comparable to a blanket lined Carhart coat. 400g would be comparable to a red quilted Carhart coat, and 800 would be the black arctic quilted carhart coat. I hope that will give you some idea which way to go.
Moisture management is the key to warm feet. Stuff the inside of those boots with news paper after the hunt and change out before bed. By morning they will be much dryer than if left to there own devices.