Is there a way to fix the black screen that happens inside the volcano in LLL after you collect either of the 2 stars? I've collected all other 118 stars and only those two are left.

no, there is no really way to fix that. that´s why 118 star is a category instead of 120.

call me crazy, but what if someone found a wrong warp of some kind? would that have a possibility of entering the volcano without crashes?