Hi.
I'm not thrilled about stacking off but I think it's fine. Besides, you bet way too large on the Turn and you are almost certainly committed here at this point in time. You only need to call $2.20 more to win a pot of $11 so you are getting around <20% pot odds.
Would i have folded if I made smaller F and T cbets? Probably not. Even though the board is so coordinated, I think sets and two pairs are much likelier to raise the Flop. This leaves him mostly with straights like 97s or Q9s which may/may not be in his range.
I do think he could be capable of making some protection plays with hands like AJ, and he doesn't want to give you a shot at improving with hands like KQ/AK/AQ.
Thanks.