He's just beautiful and I am sorry for both of you that he has been having a rough go of it. I'm SO relieved that the tests came back negative. It bothered me that your vet was so focused on a possible IBD diagnosis, but didn't want to confuse things too much with posting here.

You're absolutely right that it isn't at all unusual for a snake to refuse to eat while undergoing antibiotics treatment.

If you do have to tube feed again, you might see if you can get your hands on some Oxbow Critical Care/Carnivore. This was a standard emergency feeding solution we used for birds of prey, snakes, lizards, any pure carnivores and many omnivores when I worked in exotics practices and rescue. It's good stuff and your vet may well have it on hand. If not you can get it on Amazon.

Best of luck to you and keep us updated. I'm just so happy he hasn't been diagnosed with one of the fatal viral disorders; there's real hope that he can get past this and do just fine with you.