Yes, this sentence is grammatically correct. Nothing much means the same as a very little bit or not very much. We use it to show emphasis on a small amount. Else in this case means more. So the person is saying that that there isn't very much more that can go wrong.

Hi, in this case, we don't use "nothing." It's not grammatically correct. Instead, you should say "Not much else can go wrong at this point." I hope this helps! :)