When to call with a draw HU

[bcubed72]

Hi! I'll post the history then go into my rationale for betting the way I did.
Hero: $2598
Villan: $3402
Villian posts $150 (SB)
Hero posts $300 (BB)
Hero dealt A [img]/images/graemlins/club.gif[/img] 3 [img]/images/graemlins/diamond.gif[/img]
Villian raises to $600
Hero calls
Flop: 5 [img]/images/graemlins/heart.gif[/img] 4 [img]/images/graemlins/club.gif[/img] 7 [img]/images/graemlins/club.gif[/img]
Hero bets $444
Villian calls all-in $2802
Hero calls all-in $1554
Turn: J [img]/images/graemlins/spade.gif[/img]
River: 6 [img]/images/graemlins/diamond.gif[/img]
Villian shows AA
Hero wins $5196
Ok, now to the thinking behind the bet. Villian's min raise, in HU play, means he could have many different hands. With a reasonable chance I'm ahead, I call (I don't reraise just in case he DOES have a monster). When 3 babies come on the flop, I figure he probably didn't raise w/ small cards (unless he has a set, in which case I'm SOL), so I bet, hoping I'm still ahead.
His reraise really dissapoints me. I'm now quite sure I'm behind. Before I fold though, I think: if I fold now, I have about $1500 against his $4500. I need to compare my chances of drawing out against the chances of winning if I fold. I've got a gutshot to the idiot end; if he doesn't have the 8, I'm golden. Also I have the A, which I don't yet know is no good. (Ignore the backdoor nut flush draw). Figure 2 of my 3 outs to the A are good and 3 of 4 outs to the gutshot. That gives me 5 outs w/ 2 cards to come; about 22% probability.
If I win, I get villian w/ around $800: I'm willing to bet my chances of winning are at least 90% (obviously, if I lose, it's 0%). So the question, as I see it, is NOT am I geting pot odds; it's do my odds of hitting and winning the tourney exceed my odds of folding and winning: hence, are my odds of winning after a fold greater or less than about 20%?
My HU play is not my strong point, and my opponent is at least as skilled as I (although he doesn't seem to bluff enough). I figure my odds of hitting and winning are at least as high as my odds of folding and winning, so I call all-in.
Do you agree or disagree w/ my reasoning? Obviously I didn't know he had AA (although I suspected SOME pocket pair when he went all-in with 3 babies on the flop). Would it still be a good call if I somehow knew I had to hit my gutshot (4 outs as opposed to 5)?