Here is inside my coop today at 10 am. Wish I had pics of the girls last ngiht but I was tooo cold to worry about that.
2x4 opening at bottom of north wall window.
opening south facing wall at rafters.
north wall rafter openings
south facing wall. hard to see but that bottom square of snow is my pop door for chickens.
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Picture #1 You could staple burlap over those holes. Though ideally you should use some hardware cloth first then burlap.
Picture #2 You could do the same.
Picture #4 I would move the pop hole. The door of course needs to be fixed to close. What it looks like to me is that you have a "draw" or draft that is "sucking" the snow in.
Ventilation should only be near the top of the coop. This way the moist heat rises and is drawn off. Ventilation holes can be covered with burlap that will "breath" enough so it doesn't block the moist air from escaping.