Some very clever and skilled work here.
Might I suggest one accessory for the latch?
Stash a pair of wire cutters inside the run for when that latch jams. ;)
Or change the latch to something that has to be manually 'locked' from the outside. The spring should hold the door closed enough to keep...
I wasn't even looking at the snow crush in post #46.
Just the weight of the roof framing and sheathing that the OP has proposed might bend the side walls.