I use the heaviest gram insulated boots I can find. I think I'm up to 1500 or 1800. Go one size big because if they're too small this leads to cold feet. I use sock liners and thick wool socks. I found some some brands work better then others. I can't tell you what brand but I know them when I see them. I will also double up the cheaper ones if thats all I have. I think the combo of the liners and heavy sock work very well.

I like you had tried everything. The heated ones seem to work well but I didn't like changing into them once in my stand. Plus the extra batteries where a pain.

If this fails to work, move to a warmer place and quit hunting on cold days.