Hello and welcome to frog Forum.

Sadly your frog has a very bad case of MBD(Metabolic bone disease) this is why he has such a large underbite. From the clamy appearance I'd say that he still has some skin layers to shed. It is recommended that any frog under 1 year of age not be allowed to aestivate because their can be complications that may lead to death. Also if inexperienced in performing a proper aestivation through conditioning the frog may die.

Anyway from the look of your frog you need to take him to a Herp Vet immediately. It is possible to save him, but sadly any damage from MBD is irreversable. The bones may begin to harden, but the distortion will remain. If he was not given supplements with his food like Calcium powder with Vitamin D3 and a Multivitamin powder then it would explain the MBD.
Do you have any Herp Vets located near you?