I am sorry to say your frog looks very sick. It would be best to quarantine him in a hospital tank with paper towel substrate. If you have other frogs watch them closely if they have had contact with him.
I would soak him in a luke-warm 1:10 dechlorinated water to plain clear pedialyte solution for 15 minutes every other day, for a few days until he starts eating. You can also get liquid calcium drops for his regular water bowl, but only use the drops every other day, and I would use only half of the recommended amount due to his skin alterations. I would do it on the non-pedialyte days. You can try and force feed him. Some pet stores also carry reptiboost nutritional supplement. If you do the reptiboost, the pedialyte soak can be done less. The reptiboost is kind of like formula for them.
I would email Dr. Frye or take your baby to a vet asap. There is a thread here with Dr. Frye's email. Hopefully someone will link it here for you.
I'm wondering if he is a wild caught frog?
Be sure to wash your hands well before and after handling him. I used a wet paper towel well-moistened with room temp dechlorinated water to protect my baby's skin from further damage when I had to pick him up.
Anyway, I can let you know what my vet said, but she really didn't do much and was not very knowledgeable on amphibian care. It did however work, and after about a month his wounds healed and the dead skin sloughed off. I think you can heal him if you act quickly.