I'm glad the vet was able to give you some answers, and hopefully he will continue to improve in your care. You are great to give this Little guy a new loving home, and a new start.
We have a name for him now "RHINO" and we took him to the vet and he has nerve damage in his anal region so we have to put ointment on him, we have to put pampers on him or he will poop everywhere he may always have this problem but hopefully not his backend is raw looking and when the doc put his finger in him. EWWWWW, Rhino didn't even feel it is so hopefully in 2 months or so he will feel much better. He also had mange so he's on medicine for that to so that could also be the problem, so he is in good hands now. We are trying to bring this fellow back in to shape....