I don't know, what does he limp/call?
Some people do it with Q2o, but others will do it with 97s
or if he does this almost ATC, then he has more hands like QJ/J9 in his range that do have draws on this board

if I understood right you have 640 chips on the turn and 860 chips on the flop
pot is 240 on the flop

so just bet 1/4 of our total chips and ship turn
so 220 or something and the rest on the turn

and you already said you're not bluffing him because he's terrible, so just fire close to pot with all your value hands and c/f the rest
ez game