[Aceium]

If you're calling out of the SB to play a heads up pot OOP with a small pocket pair (which isn't that great of an idea) - why aren't you pushing in on this flop? You flopped a set and now you're going to fold? Then don't even play the hand in the first place.

BB could have almost any two cards that remotely hit this flop. He's representing something along the lines of a K with a high diamond here. He could have Adxd which would suck, but not likely because I think he would just call your checkraise.

His range is really wide, him 3betting you on this flop seems semi-standard considering that it looks like you're just trying to steal here - not allowing any diamond to draw. If you call here and no diamond comes on the turn, I would lead in for the full pot.