Okay, I think what I will do then is leave him alone as much as possible for the next 9 days and then try to feed him next Sunday since that is feeding day for everyone else. I'll offer something smaller than his girth, either a baby rat of 10g or a slightly bigger 17g one that doesn't have any fur on it. Hopefully he will eat then.

I'm surprised about not feeding him something equal to or even larger than his girth, as far as I was aware, for ball pythons, equal to their girth is just right or even up to 1.25 times. But maybe that's what causes so many ball pythons to become overweight.

Thank you so much for your advice, I really appreciate it. Hearing someone with more experience than me, even if you don't specialize in ball pythons, say that he doesn't seem underweight makes me feel much better. I think I'll post on here again next time I attempt to feed him on the 28th and let you know how it goes.