Oh my goodness, poor little guy! Do you know what caused the sores in the first place? Even if his teeth are fine, I imagine that if he's got sores on his tongue, eating is going to be awfully uncomfortable. Have you tried adding some warm water to his wet food and making it super mushy, like a cat food smoothie? He does have to eat, so if he's not able to ingest any food, then it's urgent, and despite the potential for more trauma, I think you'd need to bring him back in.
Those injuries were because he was so desperately trying to get out of the carrier? Was it the mesh or the metal opening that caused more damage? Has he always reacted this way to being in a carrier?