Are you keeping him in the amount of water shown in these pictures, with part of his body out of the water? Or did you drop the water just to take the pics? If it's the former, then give him some more water. Are you using prime or some other product to prevent ammonia toxicosis? With a relatively large fish in such a small volume of water, I would be measuring the ammonia in the water daily to make sure there is 0 ammonia always.
You could still attempt aggressive antibacterial treatment using Kanaplex, and either a protein-binding antiseptic like SeaChem Stress Guard or a topic treatment like biobandage.
You could still attempt aggressive antibacterial treatment using Kanaplex, and either a protein-binding antiseptic like SeaChem Stress Guard or a topic treatment like biobandage.