99 on button, double barrel and make my flush on river (5NL micro)

[rowhousepd]

I've got pocket nines on the button against a typical micro stakes fish (28 vpip / 5 pfr / 1.1 af / 55 cbet f). I've seen him limp w/ kings & weak aces before and call scary rivers w/ TP or 2P.

I raise his bet on the flop trying to feel out the strength of a possible pocket pair (or set). The turn is a third flush card, but since he just checks so I fire again. When he calls I'm thinking he might still have that overpair, but now I've got a flush draw too ... which happily I make on the river when the the fourth spade comes.

So do I fire again w/ a mere 9 high flush? Did Mr. Calls-a-lot just hang in there w/ AXs or KQs and has me beat? Or did he just call me w/ JJ or TT and will call w/ a pair?

Full Tilt - $0.05 NL - Holdem - 9 players
Hand converted by PokerTracker 3

LP: $9.02
CO: $6.98
Hero (BTN): $5.00
SB: $6.15
BB: $7.59
UTG: $5.00
UTG+1: $1.75
MP: $4.91
MP+1: $7.79

SB posts SB $0.02, BB posts BB $0.05

Pre Flop: (pot: $0.07) Hero has 9 9
fold, fold, MP raises to $0.15, fold, fold, fold, Hero calls $0.15, fold, fold

Flop: ($0.37, 2 players) 4 2 4
MP bets $0.30, Hero raises to $1.00, MP calls $0.70

Turn: ($2.37, 2 players) 3
MP checks, Hero bets $1.30, MP calls $1.30

River: ($4.97, 2 players) 8
MP checks,
Hero....?