I had a similar thing happen to my rooster about a year ago. My brother brought his dog over and it killed two hens and bit Bob's tail off. When I found him he had a hole in his back, and when I picked him up it sounded like it punctured a lung. I really thought he had no chance to survive, but decided to try. I put him in a cage in the garage. I put something called Wonderdust on his wound. I agree watch the wound closely, but I never cleaned the wound or put anything on but the wonderdust and bluekote. After reading some posts, I gave him Gatorade to drink--he liked the red kind. I had some left over antibiotic that I mixed in. I just tried to make him comfortable. I really thought that he would not make it, but every day I came home and he was still hanging on. He did not eat anything for quite a while, but finally ate a bit. He just sat for about a week, week and a half, but then he strarted moving around a bit. Two weeks later he was limping around with a huge hump on his back. Now he is fully healed. I think it was amazing that he survived--but God gave astounding healing powers to nature.
Best of Luck to you.