Tea tree oil can be very dangerous if used in not proper concentration, if you are to use it melafix should be used.

awesome news! If he is eating the things are going pretty well. Don't know much about care, I'll cover veterinary part. If you are to keep him, you will need to treat him for parasites that all WC frogs carry and adapted to live with. In captivity it's a different story and it will become a problem sooner or later

If he is eating it would be very good if you could find reptiboost ( reptiaid) by fluckers and dust crickets with it. It would help him heal better.