Is it a crow? It might be a fledged baby. Looks really small to me, which is what made me think that.
They are really clumsy when they fledge, I found two (years apart) when I was a kid which seemed to have broken wings. I kept them for a few days and fed them and both seemed to get stronger and were able to fly away. Hopefully this guys just shaken up as well.
Sorry, reread your posts.. If it's obviously broken, he probably would be put down. If you want to keep him, he could possibly have a decent life but with a HUGE ammount of patience on your end. For one thing, he's not likely to get tame soon. He'll need a much bigger cage or freedom in the house, and that's a BIG bird to be running and pooping around the place.. Nobody would blame you for not wanting to go through all that.
Best of luck to you, whatever you decide. I just recently lost my second starling and was completely heartbroken.. It's a heck of a thing trying to help them.