He seems to be in reasonably good shape and is exploring the tank. He can see his reflection in the bottom glass and is trying to work that out. In a few days you can add the gravel and see how he goes. The gravel will stop him seeing his reflection and he should act more normal.
I didn't even notice the dorsal fin, but if that happened when you moved him, he might have been stressed and in pain. This could have contributed to his behaviour.
As long as the dorsal fin doesn't appear to be infected, just monitor him and start adding things back to the tank. Do the substrate first so it covers the bottom. Then wait a few days to a week and see how his breathing is. If it's fine, then add another item and monitor his breathing.