Why not bet the turn here? Your hand is super strong.

On the river it's tough. Your hand looks really really weak, and almost like some midpair or spades. Unless he was slowplaying turn, the only hand that makes sense now is 6's full and maybe A6 sometimes.

The fact that he just bluffed you big previous hand though makes this though, if you hadn't said that I would definitely call this given what our hand looks like.