Re: Very skinny ball python
I'm so glad this cute little guy is doing so much better! My problem eater baby boa just ate f/t for what was only her third meal with us, which was awesome since I have the same kind of drive to get live fuzzies/pinkies as you (also, she's on treatment for a mild RI, so I'm very pleased that she's eating despite how mad she is about the daily injections).
If he's eating multiple pinkies & fuzzies, at some point you could try offering an f/t along with the live ones. I didn't wiggle the f/t for the baby boa or anything since that just seems to freak her out and she'd rather just eat completely alone with it left in her hide. I probably would've waited longer to switch her if it wasn't such a difficulty to get live pinkies and fuzzies, but she's apparently dropped her requirement of "must move" anyway and is only on "must be completely unseen when I eat" which I can definitely work with. Hopefully your little one will do the same now that he's decided food is a good thing!
Re: Very skinny ball python
When you try f/t - just make sure it's warm when you offer it , a hairdryer is great for that , if refused give it another quick blast and offer again immediately , keep repeating the process .
Appogies if you know all that :)