Michael, how do you even know its HITH? hmmmm? because it has pores on the head, just like every healthy oscar on the planet? Think before posting things about diseases. You need much more info about that subject before making a diagnosis.
A bigger tank is needed, a 55 would be ok, bigger would be better though. Feeders are a bad idea, especially goldfish feeders. If he won't eat the pellets, starve him for a few days and try it again. If he still doesn't go for a week without trying to feed him. You could also try using some frozen mysis shrimp, much better food source than feeders.
Luv, your oscar needs a larger tank as well, they can get that big in 10gals and no they do not grow to the size of their tank.
A bigger tank is needed, a 55 would be ok, bigger would be better though. Feeders are a bad idea, especially goldfish feeders. If he won't eat the pellets, starve him for a few days and try it again. If he still doesn't go for a week without trying to feed him. You could also try using some frozen mysis shrimp, much better food source than feeders.
Luv, your oscar needs a larger tank as well, they can get that big in 10gals and no they do not grow to the size of their tank.