I've had many chickens over the years, and sometimes the sick ones just miraculously pull through - so I've never culled one that was ill. On the other hand, these things tend to work themselves out. More than once I've worked feverishly to save a beloved bird, only to wake up in the morning and find it deceased. We cry for awhile, have a burial, and time heals. I really hope you have a positive outcome, but time will tell. I'd just be sure to keep him warm and comfortable tonight...take comfort knowing you've tried your best.