Take this as opinionated because it's just my opinion, I do understand the frustration of a sick snake, and you have been dealing with this for a while now.
But
If the vet can't get it better in your care, I don't see where surrendering him to a/the vet is doing Mars any justice. If you want to rehome him
maybe look for a rescue group in your area that can try to keep treating him. Maybe someone on the forum can direct you to a group?
Just a thought, Sorry I can't be of any help
Good luck with Mars