If im in villains seat your line looks painfully like something that doesnt contain an Ace - however id expect him to river shove if he was bluffing - while instead his river bet screams call me (and from my notes on him he just isnt THAT good) which makes it a clear fold.

However, Fnord keeps saying you should go with your gut more and my gut says call this because you see something made preflop - like TT- KK

Stax - ive seen this guy 3bet 22 from the SB so hes certainly doing it with 99 >75% and probably a fair few occasions with 66