HHmmm....where to begin. Lets start with a couple questions I guess. You stated that hes in a 33g tank....I assume a flat back hex. How big is your oscar? Next, you stated that you used a tap water cleaner??? Do you mean a tap water conditioner? It is very important to remove chlorine/chloramines from municipal water. The cloudeness of his eyes tells me that there IS something in the water he don't like. Normally its an indication of a chemical burn of some kind....be it amonia, chlorine, excessive nitrate ect... Melafix is a decent broad spectrum treatment, but its not a cure all. Melafix is very useful for repairing damaged fins, or keeping fungus from forming on the fish, but its not very useful for parasites or other microbials.
It does sound like you have a very sick fish, and I wish I could be more specific, but without being able to see the fish, I can only speculate, and try to give you a broad based answer. First, go back to your LFS and get some ammo chips, or amquell, or something simmilar. You want to keep the amonia from building up in the tank. Since you did a thourough cleaning on the tank, there will be no bacteria present to convert the amonia, so for now, its best not to let it build up until hes strong enough to take it. Next, double check the dossage of the malafix. Though I've come to understand that its hard to overdose that stuff, try to make sure the directions are followed closely. The addition of salt was a good thing, but keep in mind, that salt will not have to be re-added unless you take water out of the tank.....1tbs per 5g for treatment is fine. Look at your bottle of tap water coditioner and make sure its effective for the removal of both chlorine and chlorimines....if not, get one that is!! Also, it may be helpful if you turned the heat up on the tank a bit. Try to get it up to 82 degrees, but please do it slowly. A degree or two every hour is fine.
Now, this is an important part.. When you go back to the fish store, often times a paniced customer will buy just about anything to try and aid in the recovery of their fish. DONT! Do not add any other treatments to that tank. Medications are often very stressful to fish, and can compound your problem. Things like acriflavin, nox-ich, formalin are all very potent chemicals, and often do just about as much harm as good. It seems to me that your fish couldn't handle much more stress at the moment.
Leave the light off, try to keep traffic in the room to a minimum, and hope for the best. I wish you luck, and if you have more questions, or problems with him, please feel free to drop me a PM and perhaps I can try to advise further.
Best wishes,
"J"