Hahahaha. Well, I'd love to talk to you about it! I was actually thinking of rewatching it and then doing a rewatch of The Kids Are All Right, When the Levee Breaks, Lucifer Rising, and uh, I forget the name of the S3 finale ep, and then write up my thoughts!!
I thought about it the entire way home, and I think it's a mixture of two things!

1. Dean isn't being consistent with those episodes you named. One of the powerful aspects of "When the Levee Breaks" is how Dean, the real Dean, is saying something consistently contradicting to what Sam's hallucinatory Dean believes. And Sam believes that this hallucination version of his brother would call him a monster. However, the one time Dean slips close to that mindset, Bobby kicks him in the face. Dean is the one with the bravado, the idea that they can and will be able to be Team Free Will, with Sam being the one to make the bad choices. And this continues into his ACTUAL voice mail in "Lucifer Rising."

However, in "Sympathy for the Devil," Dean seems to turn this onto its head. I honestly believe it's inconsistent writing. Dean has always been the one who will fucking do this no matter what don't you believe it, and it seemed a little strange for him to already snap and blame everything on Sam. I think, as a writing decision, it's been pretty consistent in season five, but it's not consistent with anything you mentioned prior.

What is consistent is Sam's writing. Sam's need to do this, Sam's need to cling to Dean and gradually become the more dependent on of the two in incredibly unhealthy ways. Sam needs Dean to believe in him, and the reason why he went ahead and killed Lilith, instead of finding Dean, was because of the altered voice mail. Like, he did a lot of fucked up things in that episode, but it was that final moment that really set up Sam to make the mistake.

I think the Dean we've had in S5 has been someone who is acting like he hasn't lost anything, can do things, and is talking a lot of game. But it's not completely consistent with S4, unless the trigger was Lucifer Rising all along, and with that happening, he realized he couldn't keep up a front.

2. Dean has always had a lot of bravado and is actually giving up. It's just surprising that he hasn't yet. I believe this might be what they're going for if we're saying that the writing has been consistent. All the way back in S2, in Croatoan, Dean told Sam that he was tired, he was very tired, and all he wanted to do was live a normal life. I think Sam knows this, which is why he used that as his trigger in S4 to start drinking demon blood, even if Sam was already so gone from needing a normal life it wasn't funny. I think saying Sam was thinking of Dean--well, it makes sense. And if you think of how uncomfortable Dean was at Adam--or ghoul!Adam--learning how to be a hunter, you can really pay attention to how he just really wants things to be ideal and idealistic and happy.

If you think about it, this isn't the first time Dean has given up. He gave up in hell by taking up the knife and starting to torture those guys. Yes, that was after thirty years, but Dean doesn't have the same resolve as his father. He cleans up his father's messes, but he's not the same stubborn jackass. Well, I think the fact that he DOES clean up John's messes is exactly WHY he is not the same stubborn jackass; Dean is ... well, I don't want to say weaker, but his ideals are different, at heart. Dean wants happiness, wants things to be better, wants a perfect painted picture, and he hates having it thrown in his face that these things will just ... never be. And he can't handle it!

What I think Dean wants is for things to be okay, but we've been moving toward this loss of him being able to fake it. In My Bloody Valentine, Sam has the issue with the blood at the end and Dean has that slip of hope, and it just keeps growing as the episodes go by. It's not that he wants Lisa to be ideal, but it's that she's the only thing that's untarnished at the end. Sam is ... Sam is what Sam is right now, Castiel is a poor example of an angel, Bobby is in a wheelchair, and what we have with Dean is basically having everything BUT this ideal being fucked up.

So, it makes sense he went to her, went to preserve the one thing that hasn't been fucked up.

What I find interesting from a perspective of a viewer is that up to My Bloody Valentine and including that episode, we were led to believe it was Sam who would slip. But Dean was faking all along, including in Free to Be You and Me, because he has to try hard, has to act like he's okay, even if he's everything but.
Well, I do understand why he went to her, why he left and so on! The hints were all there for Dean to just... not take it anymore! I think it was Lisa's reaction to what he said that I found a little odd (I NEED TO REWATCH IT THOUGH I'VE ALREADY FORGOTTEN WHAT THEY SAID)