My feet are slightly wide, all the way down, but very thick. These boots are the only ones I’ve ever found that actually fit well, probably because the boot itself is very flexible and malleable.
I don’t know if they’ll fit your “extremely wide” feet, though. They do have a few sizing guides that might help you answer that question?
That’s probably a bit colder than what I’ve shown them, probably around -25 to -30 at the coldest. I would definitely not describe these things as warm, and I definitely have “winter socks” that I wear with them. Even then, my feet will get cold unless I’m at least moderately active.