I don't know what to tell you. Those symptoms are strange. I just want to provide some support. It sounds like that animal was abused before you got him. You are a saint for trying so hard to make him better.
I feel for you, as my very first snake (bought from a major pet company) died within 2 weeks. I did not have enough experience to know that something was wrong. I got up one morning and he was dead.
I now have a super healthy snake named Harvey and he is a certified therapy snake. He swims at the beach with kids, he visits kids in the hospital, and he is a regular at the dog park. Just telling you this to put a smile on your face.
Your situation is terrible and I would be very upset with the seller.
You have all of my support.
Merriah and Harvey