Personally, I would shoot the fox if they came near the coop, but if you don't want to do that, get a good dog. We have lots of foxes in my area, but I've never had them near the coop. The dog is indoors at night, but they seem to keep their distance anyway. Hawks have been a much bigger problem for me. I've had them attack chickens when I was outside with them, but ~100 feet away.
I keep my chickens in a chicken tractor, and let them out only when someone can watch them. The dog would work, but she usually gets distracted with other things, so we don't rely on her when the chickens are loose. At night, I close the entrance to the coop with a gate covered in 1/2" wire cloth. Nothing big enough to hurt them can get in.
Good luck with your injured birds.