Moving up limits to chase losses, first trouble hand

[donkeykong2]

So i move up in limits to 25/50c after being down a bit in the 10/25c on pokerroom. I go to a 3 handed table and the first hand comes like this. i dont have the hh right here but i remember pretty well it went like this:

BB folds, SB limps, I raise to 2 preflop from BB with K8 offsuit, SB thinks and calls. Effective stacks 50$.
Flop: 8,5,2 rainbow
SB instabets 4, i think and call
turn: 10, SB overbets pot 15, i think and call after some consideration, the 10 put some kind of flush draw on the board.
riverffsuit 6, SB moves all in for around 30 more, what do you do here?

my thought was, that he was pretty weak preflop and his instabet on the flop was little suspicious too, 52 would be possible, maybe he made 2 pair with the 10. overall i can only beat a bluff, but his line just represents nothing but highly unlikely hands. what would u suggest here? sry for the possibly bad language. [img]/images/graemlins/wink.gif[/img]