Some update:
We tried a a warm sugar water bath and that didn't help.
Gecko passed more stools and one of them was a huge braid-like wrap of superworms. So I think that's where I messed up. In trying to get the gecko to eat (which was probably just him needing time to adjust to the environment) I tried different foods and with the superworms he gobbled them up and I think I gave too much. And I read now that they are hard to digest. In the stool the superworms looked almost completely intact.
We couldn't afford the vet bill (we just so happen to have a lot of co-occuring financial hardships right now) so we found a Reptile Zoo that takes sick reptiles as a rescue and we surrendered it there.
Sad timeline of events and it's hard for my son, who is 9, and the gecko was very cool to have and interact with and I feel terrible and all of those things. Felt I was trying my best and to be informed but obviously wasn't enough.