Sorry I live in Scotland and had to go to bed. Even if he doesn't make it, you tried your best. But by the sounds of it, he still has a chance. Keep us updated!
Ok I don't know if she's coming, could you open a window instead? I would avoid bringing in another hen, you never know, things could get nasty. But how is she doing just now anyway?
I'm not sure, but could the illness spread? If you are certain it's only wounds, maybe take him outside, I'm not %100 sure though. Don't leave him unsupervised if you do decide to take him out.