Hi Victoria
I read your post and had a few thoughts for you.
Baby savs are pretty rambunctious and fiesty. Thats a good sign. As far as them sleeping a lot....they do laze around if there is nothing for them to do. Try changing up the tank every now and then and I'm sure he'll explore it.
I wouldn't worry so much about the crickets or wax worms either. Savannahs are tough and built to hunt. They'll often take on prey that we would think is too large for them....but what do we know
It sounds like your guy is around 6 inches TL from your description so he's more than big enough to handle crickets and mealworms.
No need to feed him outside of the enclosure either. If your husbandry is decent, a little ingested dirt means nothing.
If you want to read more about them there is a book available from me thats got all this info in it.
Hope this helps and good luck
--Ravi--