Actually, I think when Kristy left Sam's hotel room, she wasn't possessed. She acted differently (yeah I know it could have been on purpose but it DID feel like an entirely different character), and it didn't seem like Samgot her name wrong on purpose. It kinda felt to me like then, she was just a one-night stand but when she entered the diner afterwards Sam just immediately knew it was Ruby because...who else could it have been?

Very possible. Of course that would indicate another kind of darkness though one that I can handle in that Sam doesn`t call her on possessin random girls (whom he slept with). Would be quite a twisted game if they did it often.

I might actually read Dean/Castiel. No kidding.

I`m sure it`s being written right now. :D