Husbandry sounds pretty good!
Your gutload could use some improvement IMHO. I feed my crickets a wide variety of greens (dandelion greens, collards, kale, endive, romaine lettuce (it has good levels of calcium, etc.) and veggies (sweet potato, white potato, squash, carrots, red peppers, etc.) I have never used "happy cricket" so I can't tell you if its good or not. I also have no idea what "dragon dust" is and I've never used the pellets either.
You said.."he has always refused to eat fruits or veggies tried all types"..I know so many people who say this and I can't figure it out. Mine have always eaten lots of fruits, veggies and greens. I can't understand why mine do and many people's don't.
You said..."he does poop"...that would lead me to believe that he has to be eating something...and shows that he isn't impacted.
I'm wondering if his mouth is too sore to eat much?
Do any of the things that you feed your insects or dust them with or the pellets contain preformed vitamin A (not beta carotene)? To me, the way the mouth looks would lead me to feel he has MBD....but as I said before, I'm not a vet, so its just my opinion. Vitamin A and Vitamin D3 and calcium are the three main players in that...and since you said that he gets calcium on the crickets and he gets direct sun, that only leaves Vitamin A.