Definitely fire again on the turn. The 5 doesn't help his range much.
The river bet is a little thin imo because pretty much every A in his range has you crushed. I'd have to have a read villain could call a vbet with an underpair like 77, 99, and 66. We can discount 99 since we hold a 9, so really his underpair range is 77, 66, and sometimes he'll show up with JJ. I can only guess villain would raise most of the time with JJ and every time with QQ and KK.