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...