How about a temporary garage. Just leave the side open where the light doesn't shine and get some fans to help with ventilation. Sorry you have to deal with this.
I have the same thing with my chickens except it is just one aggressor. I isolate and reintroduce every one to 3 weeks. It seems to get better, but not resolved as of yet.
It is exactly what I am dealing with. You have a bully in your flock. Find her, put her in "jail" and it will save the others. I am using saddles with the injured hens until they heal ( the others started pecking at the exposed skin and blood). They are starting to heal and it is also more...
I got a 50' x 50'. They do make bigger, but I'm not sure how much. Your chickens are very fortunate you have that much space in your run. Yes, snow will fall through it and it is very durable. I did upgrade from zip-ties to hog rings because I heard the zip-ties will deteriorate.
We have every predator one can imagine:hawks,owls,bald eagles,bobcats (seen on security camera),raccoons,opossum, foxes(family), neighbor dogs, cats, etc. Although I have never seen a weasel, I've heard you don't see them until they get your chickens. Therefore, I need Fort Knox-type...
I use a mix of oats, cracked corn and black-oiled sunflower seeds. (grit/oyster shells always available, of course) Works great. Also, feed them protein every day. Mix in a little DE in the summer, too, to prevent worms. Got the idea from "Becky's Homestead" (YouTube) So far, so good.
Just started with chickens March 2020. I have been reading and getting great info from this forum since before March 2020. Now that I have a little experience, I thought I might be able to contribute. Appreciate all that I have learned and look forward to learning a LOT more.