Star...I'm often a bit too aggressive for my own good to begin with, so take the following for what it's worth.
At some tables, I think an MP open-raise with KJs is a fine play. Toward the LAG end of the spectrum, I suppose, but not overly so. The problem here is that, as you said, the player on your left seems to be obsessed with 3-betting your raises. This means it's possible that he's even doing so with a worse hand than you, but in general he's probably got you beat, and he's got position. So an open-raise here seems to be asking for trouble. (Nevertheless, I'd still do it because, heck, I really like raising
)
On the flop, I think there's absolutely no question you're taking it to the river...and, I think your draw is strong enough to be played aggressively; even if you miss your draw, you may get him to back down and fold some AK-AJ sorta hand.
Of course, there's plenty of ways to play aggressively. Personally, I think I would've check-raised the flop and leading out the turn. If he 3-bets my checkraise, I'm willing to believe he's got a big pair and just call down and hope to hit my flush/gutshot. I think the problem with your line (calling flop, leading out on a scare-card) is that it doesn't look too convincing. Any time someone pulls that move on me (i.e. cehck-call, and lead when the bottom card pairs), it makes me about 95% certain that whatever their hand might be, it's not what they're representing.
I guess what I'm trying to say is that even though you got a big draw, you'd much rather see him just lay down something like AK or AQ without having to hit any of your outs. Leading out on the turn after check-calling the flop is one of those confusing plays that often triggers your opponent's "calling reflex" (A Mike Caro term, by the way)...the bottom card pairs and you bet, but he knows you probably don't have trips with any hand you'd raise...so he'll think you're trying to bluff him off and call you down with his AK. I'm not saying that's what he had this hand, but I just think your fold equity is a lot higher if you throw out a check-raise on either the flop or turn, as opposed to the stop-n-go thingy.
Just my thoughts, anyhow.
-TW