Update:
The Mouth Almighty has successfully been feeding reliably on ghost shrimp, and so has the Datnoid. I'm probably going to end up clearing out one of my nano tanks and reestablishing it as a ghost shrimp breeding setup; shouldn't be too hard as I've kept ghost shrimp in the past before and they bred like rabbits. Unfortunately, the datnoid has somehow gotten ich and I have isolated him in a temporary 5g quarantine setup; luckily the main 75 growout doesn't seem to have other ich-ridden inhabitants and I successfully isolated the datnoid at the start of the illness. The datnoid is also still greatly interested in food, and other than having some difficulty swallowing ghost shrimp (he had the shrimp in his mouth for over three hours; still managed to gulp it down though) and lethargy, he's doing well. Still going to have to treat the main growout tank regardless, though- can't really risk losing any fish from ignorance. What's slightly worrying is that this is the first time I've had to deal with ich in ~2-3 years or so; last time I had a major outbreak and lost nearly all of my plecos and Mastacembelids, and I fear that I may end up losing the Dat and Mouth Almighty (although it's probably rather unlikely).