First~Danzo has got a secret plan of either becoming hokage or eliminating akatsuki or both (He doesn't seem to be with Akatsuki cause he killed the messenger frog who was supposed to call the 9 tail jinchuriki) Danzo may assasinate Tsunade but he wouldn't do the same with the elders, afterall they are his allies.
Second~I hope Might Gai saves Kakashi's butt in this fight. Good news would even be better if he played a major part in revealing Pain's secret and bad news would be exactly as you said, we don't wanna see him lying in bed again.
Third~What are R. C. cars? Its possible that the secret of Pain (or real Nagato) is in the Rain village. Pain wouldn't be so unwise to keep his secret unguarded, there are also rain shinobis who protect the village. What if real Nagato resides in Rain village and has got some really good powers?
Fourth~Very possible. Also maybe Sasuke's main target would be the elders and Danzo.
Talisix had well written what he/she thought, I just added my thoughts to it.