And thank YOU for taking in this poor little 'dumped' snake...

Snakes that bite themselves sometimes are suffering from intestinal parasites...have you ever gotten a fresh stool sample -his, of course - seen by a vet?
Parasites grow more numerous when food is increased, but can eventually cause regurges & even death of the snake: be careful how fast you de-worm him,
IF the vet finds that to be an issue...as a sudden large die-off of internal parasites can block off critical internal organs & therefore cause them to fail. I've
had good luck in the past using repeated but lower doses to de-worm snakes...as in, "better safe than sorry".

And hopefully this (parasites, aka "worms") isn't the case at all, but it's just another possibility that I would recommend looking into. His regurge isn't limited to
only one cause anyway...just want to cover all the bases here. All the best with him...that's so cool that he's got so much room to roam in his enclosure.