That is probably the reason he won't eat, try feeding him a live mouse or rat in his enclosure. Removing for feeding is unnecessary and stresses them out. UTHs do get very hot, that's why a thermostat is necessary for them. I suggest switching back to the UTH and get a thermostat for it to regulate the heat. An ASF is an African Soft Fur, a type of prey. They tend to go for them if they are picky because they are what they eat "in the wild" I believe, there are breeders here and there for them. It's usually what people will switch to if they cannot get their balls to eat.
what about tank aggression?
Reptiles
0.0.1 - Rhacodactylus Ciliatus, Cheerio
Mammals
1.1 - Canis Lupus Familiaris, Little Man & Molly