Definitely sounds like a dire situation...
Maybe try some live food ie..hermit crabs,snails and even a pep shrimp ....
Maybe try a scallop and krill tied onto a thread or fishing line and just let it dangle in there...I would not try netting him anymore or even putting your hand in the tank,,thats causing a lot of stress
I sure hope he pulls through for you ,,I love mine, they are my favorite triggers
QTing is a good thing
Grow your filtration