Two Plus Two Older Archives - ideal flop, only behind very unlikely hands

$1000 Pot Limit Party
(a bit above my level. i belong down at the $400s probably, but within by bankroll)
my image: probably a tiny bit laggish, but nothing way out of line, probably 28/8, maybe little lower due to higher than normal stakes, and probably seeming less laggish because of how aggressive the game is in general

villan: only been sitting for a little while, no reads as there's been nothing out of line so far and i'm watching TV, not enough hands to make the VPIP/PFR significant.

i'm UTG with $950 and am dealt: 4[img]/images/graemlins/spade.gif[/img] 4[img]/images/graemlins/club.gif[/img]

I limp, all fold to CO+1 who limps (roughly same stack as me), SB completes, BB checks

flop ($38): 2[img]/images/graemlins/heart.gif[/img] A[img]/images/graemlins/diamond.gif[/img] 4[img]/images/graemlins/diamond.gif[/img]

i lead out for $30

villian makes it $90 (~half pot)

in my mind i put villians most likely holding at decent ace or maybe A2s or even better 22. I put AA as unlikely enough to not worry about it.

I raise slighty less than pot to $275 straight (~85% pot)

He makes it $600 (little more than half pot)

let's ignore for a minute the fact that i threw the rest of my money in the middle gleefully.

when he put in the third raise i had already decided to get it in as fast as possible, and rationalized it with the idea that he could be semibluffing diamonds or much more likely playing his bottom set as fast as i was playing mine.

clearly my final push has no folding equity, though he also will have to call with all of the hands i'm still beating.

my impression is that the mantra "don't go broke in an unraised pot" is meant to warn against things like junk straights from the blinds, and probably playing strong hands like sets weakly in fear of this very occurance will cost you more than you save when you don't get crowbarred by a random hand.

but the third raise, had it been full pot, would have put both of us effectively all-in, which means his half-pot third raise should eliminate overplayed semibluffs like 5[img]/images/graemlins/diamond.gif[/img] 6[img]/images/graemlins/diamond.gif[/img]
He also has to fear the AA, because UTG it's at least conceivable i could have it, especially in Pot Limit, i just can't see him making this play with 22 either. But can i be more sure of either of these reasonings than that he wouldn't have limped in MP3 behind a limper with AA or god-forbid play 53?

The fact that we both started the hand with roughly 100BB let's me think that i should be able to go to the felt with middle set guilt-free on a pretty benign flop. But the fact that there were only two limpers meant the starting pot was a bit more than 4% of our remaining stacks, and had there been two more limpers any third raise on the flop would put me all-in and there would have been no room for additional information.

As much as i don't want to do any results oriented thinking, i can't help but think the half-pot third raise to 600 should have let me let it go, however unlikely the preflop action made it seem that i was ahead.

thoughts?

results:
<font color="white">
turn: 2 of diamonds giving me the full but him the straight flush. </font>