1) Yes, I think if he gets in a situation where he needs to, he would. I don't understand why people are so quick to say Sasuke wouldn't kill Sakura (hoping for them to get together at the end, probably >_>). Sasuke's bond with Naruto has always been portrayed as far stronger than any bonds or feelings he may have with Sakura, yet when the pair where first reunited in Shippuuden, at Orochimaru's base, Sasuke was quite prepared to take Naruto's life.
Why? Because what Naruto wanted to do (taking Sasuke back to Konoha) would get in the way of the revenge he desired.
Now Sakura's trying to do the same thing, by preventing him from getting vengeance on Danzou, the man that pretty much ruined the life of him, his clan, and his older brother. Not to mention, Sakura's supposedly prepared to raise her hand against him, to do so, and that this is a far darker, colder Sasuke than we've seen before. I wouldn't rule her death out (in the sense that it seems illogical for him to do it; I doubt Kishi will kill her off anytime soon).
2) I think it's rather obvious it'd be a last straw situation for Naruto, and the nine-tailed sage would embrace his seemingly inevitible destiny to fight the final battle of Senju and Uchiha, going straight to town on Sasuke's weedy Mangekyou ass.
3) This just doesn't seem like a realistic option at all. Sakura wouldn't abandon Konoha, not even for Sasuke. Or, she would, but not for this Sasuke. Not helping Madara. Not going after Naruto. Not trying to control the world. Sakura's a clever enough girl to know her loyalty is to Konoha, and that it's time for her to grow up. She said as much in her confession to Naruto (let's face it, at least that part was real). She knows Sasuke needs to be stopped now. Feelings for him, or no feelings.