$11 A9 in blinds, rr?

Villian has raise frequently (about as much as I would).

NL Texas Hold'em $10 Buy-in + $1 Entry Fee
Level:5 Blinds(75/150)

Total number of players : 4

Seat 1:Button ( $2196 )
Seat 2:Villian ( $1333 )
Seat 3:Hero ( $2110 )
Seat 6:UTG ( $2361 )
Level:5 Blinds(75/150)

Dealt to Hero [ A[img]/images/graemlins/diamond.gif[/img] 9[img]/images/graemlins/spade.gif[/img] ]

2 folds. Villian raises [225]. Hero calls [150].

pot = 600

** Dealing Flop ** [ A[img]/images/graemlins/spade.gif[/img], 6[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/club.gif[/img] ]
Villian bets [150].
Hero?

How often can you assume the minraise was a steal, and this continuation bet deserves to be re-raised?
If I feel this is worth re-raising (900 was my choice) then why didn't I raise it preflop? Is this a better or worse line?

I think I was thinking he'd call or reraise me preflop, so I wanted to see a flop. Just puzzles me why I took comfort in that A, when it would kill me if I was dominated. Worrying too much? A9 with 4 players stronger than I'm giving credit?
Also, what about the amount? If I re-raise preflop, or raise on this flop, is 900 (3x bet) about right, or is this push territory? I felt myself confused by so many similar sized stacks. Normally it seems easy to push with a small stack or into a small stack with big stack, but felt puzzled by all the same-stacks.

Thanks for the help