You seem to be aware that this is generally a 3 betting position, esp. with all the dead money out there. I would make it $36. But as a new player oop, I could see the case for just calling.
AP post flop (other than river sizing) I don't have an issue with it. He bet into 5 players otf, which would indicate he isn't bluffing.
Checking the river to induce seems bad, since I don't think he'll bluff or bet his worse hands often enough, and you may miss value. I would bet slightly smaller to give him more of an option to call his JJ - KK type hands, but you don't want to bet so small as to under charge his Ax hands that might just call your bet. $60 seems fair.