Questions about my new Crested Gecko.?

All of that sounds fairly normals. Especially if he's a young gecko, he isn't going to eat too much. Try cutting the fruit into really small bites and make sure you get everything dusted well. Other than that, just give him a little time. Substrate and moss are usually fine and don't cause impaction nearly as frequently or severely as sand, but if you want to, you could switch to reptile felt. This can be purchased at most major pet stores. You'll need to be a little more on top of the tank humidity, as it doesn't hold as much moisture, but it should be fine. Alternately, you could build a little moisture box out of some tupperware and put your moss in their. That way your gecko can seek out the moisture when he needs it. Hope that helps, and good luck with your pet!