Poor guy...

It looks like a secondary infection due most likely to stress that the injuries have caused. I would get some stress coat for him and make sure to keep the tank water pristine. Hopefully he will bounce back. Looks like it was quite the battle and I would make sure never to put that GT back in the tank with the
JD.
The salt will do the same thing as stress coat,in that it acts as a irritation that will make the fish produce its own slime coat. But stress coat may be gentler than the salt IMO.
Also IMO I would not advice you to use Iodine and a cotton swab at this point (sorry CWO4gunner) as you will end up wiping off more of the natural slime coat that the fish produces after an injury and furthering more problems.
It may work for Cwo4gunner, and maybe on larger fish, but your little JD really should not be handled at this point with its injuries. just my opinion...