Don't fold two pair at 2$ NL unless there's a 4 straight/4 flush on the board.
Raise the flop. I don't care where villain is at, because his range includes a lot of other kings, 74, K4, K2, random junk. I suppose we can call the turn, since his bet/3-bet is a pretty strong line. However, we're never folding to pretty much any bet, even if this is a set of 4's quite often.
When you hit two pair or better, you should be looking to get all in at 2$ NL unless the board is crazy nasty. Period. This is not optional, and failing to do so is burning money. Raise the flop, and threaten their stack.