Why would you have to jettison the scene on the hilltop? I think that Dumbledore did have some of the character flaws that led him to be seduced to the Dark, but I think that he may have gotten out a bit sooner than Snape did. I also think that one of Dumbledore's flaws is being a bit blind to his flaws. I think he sometimes forgets how similar he and Severus actually are in their mistakes with the Dark. I agree that Dumbledore also lost the plot a bit and forgot about the fact that Harry (and Snape for that matter) are human and the whole love thing in his manipulations. He took thinks he knows best. I like your AU.