Top pair and big? draw

Opponent is goofy, only way I can really describe him. We both have $200 stacks. He makes big overbets, both preflop and postflop. I hadn't seen any of his hands at showdown though. What do I do?

Party Poker No-Limit Hold'em (NL$200) <font color="#0000FF">(5 handed)</font> link

Preflop: Hero is BB with K[img]/images/graemlins/spade.gif[/img], 9[img]/images/graemlins/club.gif[/img].
<font color="#666666">2 folds</font>, SB calls $1.00, Hero checks.

Flop: ($4.00) 7[img]/images/graemlins/spade.gif[/img], 8[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets $2.00</font>, <font color="#CC3333">Hero raises to $6.00</font>, SB calls $4.00.

Turn: ($16.00) 6[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets $35.00</font>