Villain has been in my grill all game and seems to be semi-loose and aggressive. should i make a stand here or cut bait w/ the over and flush draw on the board?

i want help understanding where i am +EV to call (prolly not here) in a 6max game (iow, how often does QQ win/hold up here?), or when it is not even right to call a "maniacal" player that seems to have me pegged for a nit (future table image?). bottom line is i have no problem "re-popping" him, but cant confidently put him on the draw. i figure it 50/50 that he has K-rag.

in a fr game, i get away from this 95% of the time...with no regrets. how different is 6max post flop?

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.05/$0.10
6 players
Converter

Stack sizes:
HERO: $9.80
UTG+1: $14.95
CO: $11.05
Button: $7.65
SB: $8.80
BB: $4.30

Pre-flop: (6 players) HERO is UTG with Q Q
HERO raises to $0.4, UTG+1 raises to $0.7, 4 folds, HERO raises to $2.4, UTG+1 calls.

Flop: 6 K 9 ($4.95, 2 players)
HERO checks, UTG+1 bets $1.9, HERO??

i figure i established initiative pre-flop...and he leads out anyway?! should i have led out on the flop, and folded to a raise, or was the pre-flop 3bet good enough to know i am beat here?