I think he will immediately dig a cave but jumping isnt about the cave. He can jump after having a cave so u should cover the top even a very small hole. Also they dont like crowded tank and active fish so becareful. With a tank like this he will hide all day long or jump... I love jawfish ver much very interesting fish. I think u need min. 4" sand but more would be better. Also becaruful they can easily make the rocks dropped w/ the corals on them. I think in a tank w/ a jawfish, u cant decide on decoration because jawfish will probably decorate the tank every day... Also maybe you can buy him a pair. They will live in the same cave (which is very interesting to watch) and will probably have eggs in their mouths (they have their babies in their mouths like cardinals) buy groving the babies is hard, u need rotifers.
These arent my experiences btw, learned from forums, chats and books
Good Luck
Selim