AJ on button

[RIDGE45]

Just wanted some feedback on this situation.

I have 4400 with blinds 50 100. I have A J on the button.

3rd to act raises to 300(have seen him raise with QK, etc in early position). Guy to his right calls. Everyone folds to me on the button, I call. Small blind folds, big blind folds. 1,150 in pot.

Flop comes 3 [img]/images/graemlins/diamond.gif[/img] 6 [img]/images/graemlins/club.gif[/img] 9 [img]/images/graemlins/club.gif[/img]. Original raiser checks, guy to my right checks I check.

Turn brings J [img]/images/graemlins/spade.gif[/img]. Original raiser bets 500, next to act raises to 1000. 2,150 in the pot, 500 to me. I put the original raiser on QJ or KJ maybe an overpair (doubtful since no bet on flop with possible flush draw). I have bad feeling re-raiser flopped a set so I fold.

River comes original raiser checks other guy raises. Original raiser calls showing KJ. Re-raiser shows a set of nines.

That is just the situation but my question is in my situation with two callers in front on the button would I be correct to call, fold or raise?

Also, on the turn if guy with the set had not raised but rather had called, I would have called. If he folded I would have raised, is this the correct move?

Also in general what do you guys think of AJ on the button with callers, with a raise, and with limpers?

Thanks a lot.