Sorry for the delayed update! He is actually eating just fine! He'll only eat a few chunks of earthworm every 1-2 days, but I got in touch with the breeders & they said they fed their babies every other day, so it is normal.
I have not found poop, but a few days ago I did see a large bump on his left side, & it was gone the next day, so I hope that means we're in the clear & just lost in the substrate. Lol!