OK. My 2 cents worth.

A couple of extra pairs of dry socks and gloves.
You can hang a damp pair on your bag to dry as you wear a dry pair
Heavy duty garbage bags make decent dry bags if you double bag them.
Strip down when moving, dress up when stopped.

You might need a bigger bag, winter gear is about bulk. You end up packing a lot of air even with compression straps.
It is nice to be able to stuff your coat into the bag too when you are hiking.

Yes, slogging through snow is exhausting.
Remember to take frequent breaks.

Edit:
I like to point out that mitts are warmer than gloves and an extra large pair lets you wear gloves inside them of you have to.

Edit again.
Goretex still sweats, just not as badly as a fully sealed fabric would. I would suggest gaiters to keep your calves dry if the snow is wet and breathable wind pants over decent long underwear instead of goretex.
Fleece is good for underwear, especially since good woolens are impossible to buy any more.

Sherpadog suggested fleece as a sit down pad.
I like a piece of ensolite, I will have to try some scrap fleece next time I am out, it sounds like a good idea.

Most people overdress the upper body and underdress the lower body. If you have decent lower body clothing you might find yourself hiking in your tee shirt just to stay comfortable.