Does he still have to take meds? When they need to get pills or whatever it may influence their behavior. When Filou needed eye drops he used to disappear whenever he saw my husband and me in one room. He forgot after it was over (but now he needs pills again and I am already afraid of that period).

On the other hand: a liver infection sounds serious. So it may take time until he fully recovers.

Anyway I am glad to hear the vet likes the development. So I hope the rest is coming soon