My pleco was very much the same. Driftwood is a good option, because I find most plecos take to it quickly and it doesn't go bad when uneaten like wafers.
try shrimp. when i chop up shrimp for my other fish i leave a couple intact so that they sink right away and the pleco jumps on them. a little extra darkness might help him settle in too. as for how he survived his previous nasty tank, maybe he lived off of all the tank mates that died!