Hm, if you try to feed him outside his tank again, I would try maybe a bucket or a plastic storage container, like something made by Sterilite. From my experiences with my own frogs, they aren't fond of being on towels, especially dry ones, so it could be a distracting texture.

Where did you buy your frog? Do you know the conditions he was in prior to this? Was he receiving calcium and multivitamin supplementation on his food?

If you could, try to get a clear picture of his face. His jaw looks off to me...does it look like he has an underbite? Or compared to pictures of other frogs, does it look different from normal?

Sorry for the barrage of questions, just trying to help you get to the bottom of this. From what I see, especially in the bottom right picture, it looks like there's something off with the lower jaw. I don't want to alarm you, but sometimes the inability to eat coupled with deformation indicates Metabolic Bone Disease.