It's really hard to tell from thepictures, but it's definately not velvet. Ich is a possibility, but some of your other info really does rule it out. IS the fish flashing at all? Is he eating well? and is he clamping fins at all? Are there spots anywhere on his body except the tail?
Your earlier information really does make ich seem impossible at this point. the pictures aren't clear enough to really tell for me. The fish looks otherwise healthy, so I guess I would reccomend keeping things as they are and watching him closely for a few more days. I know it's hard to get a really good photo, but if you can it may reveal something else. Also if you can get a magnifying glass you may see more that will help clue us in. There are only really a handful of ich strains that are even resistive to salt, and at 80+ degrees there are none I have heard of that will take more than 4-5 days to fall off the fish. Is it possible that the fish has a fungal or bacterial infection in the spots where the ich originally was? Many folks will claim that salt kills fungus in our tanks, but I have not found it to be 100%, and many types of bacteria are resistive to salt as well. could be a secondary infection.
Sorry I can't be more helpful on this.
Dave