55 with flopped set

[dana33]

Coming from a limit background, I am finding that one of the biggest adjustments to NL is the need to pay attention to my own stack size when betting -- so that if I'm going to be pot committed anyway, I might want to move in.

In this hand, with the possible flush and straight draws, and given the small size of my stack, should I have just moved in on the flop?

A related question: how small should I let my stack get before I rebuy to bring it back to the full $25 buyin?

Party Poker No-Limit Hold'em, $ BB (10 handed) converter

Button ($30.2)
Hero ($12)
BB ($22.75)
UTG ($24)
UTG+1 ($43.2)
UTG+2 ($100.4)
MP1 ($25.1)
MP2 ($37.25)
MP3 ($25)
CO ($33)

Preflop: Hero is SB with 5[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/spade.gif[/img]. Hero posts a blind of $0.25.
<font color="#666666">4 folds</font>, <font color="#CC3333">MP2 raises to $2</font>, <font color="#666666">1 fold</font>, CO calls $2, <font color="#666666">1 fold</font>, Hero (poster) calls $1.75, <font color="#666666">1 fold</font>.

Flop: ($6.50) 6[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/club.gif[/img], 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets $4</font>, MP2 calls $4, CO folds.

Turn: ($14.50) 3[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $6 (all-in)</font>, MP2 calls $6.

River: ($26.50) 7[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>

Final Pot: $20.50