That is wonderful to hear! Now that he is normal, lay off the tuna juice and tuna stuff- human tuna is not good for kitties.
If you want to entice him to eat and give him fiber at the same time, add catnip to his wet food. Don't worry he won't roll in his food, though he will be interested in eating it, and the catnip will give him fiber that he needs. Do about 1/4th of a teaspoon in a day broke up into several feedings.