First round of Event14, the $1,500 Shootout. 10-handed tables, but it's the first level (25/25) and only three players have arrived at our table.
Only about 20minutes into the level and no significant hands yet (especially as we have a tremendously slow dealer). So all three players have essentially the starting stack of 4,500.
In the hand, I am the BTN, and the other two players are the SB and the CO.
CO limps, I raise to 100 with K

8

and SB calls, CO calls. Pot 325.
Flop A

9

9
Checked to me, I bet 175, SB folds. CO calls. Pot 675.
Turn 5
CO bets 250. I raise to 850, hoping I can win the pot here, but with the NFD as backup.
The CO thinks for quite a while before making the call. Pot 2,375.
River 4

so I get there with the nut flush.
CO player checks to me. My best action now ???