Along the subject lines, I bought a pair of Mickey boots many years ago, the first time I wore them treestand hunting, my feet froze. Needles to say I was bumed out, when one of my friends saw them, he commented, where are the insoles ?, so that the sweat has a place to go. I said they don't come with any and, I figured that is the way they are to be worn. I got a good pair of LaCross inner soles and that was the ticket.
Of coarse your socks have a lot to do with it also, I wear a pair of good smart/marino wool with a wicking sock also usually made of fleece, and they CAN'T be tight in the boot ( whatever you wear ) they must have room to breath. I'm not saying the boot has to be loose, just not tight.
Hope you find a system to help you keep warm.