In case you don't know about this- it can help you find an experienced herp vet: https://members.arav.org/search/custom.asp?id=3661
I know that in many areas, they're as "rare as hen's teeth".And sick snakes can be very frustrating-
If he's in the neighborhood of 10-17 years old, I think he's also getting up there? Hoggies are awfully cute, but I had poor luck with them when I had a pair many years ago. That's great that you were there to take him in & give him a better life.