Why is Tobi so protective over Sasuke then? Why does he need Sasuke for his Moon Eye Plan, he saved his life when Onoki was about to kill him, he wouldn't let Kabuto get him, why does Tobi need Sasuke? The only explanation for that is that he is Sasuke, and if Present Sasuke dies, then so does Future Sasuke. Sasuke being able to time travel would explain a lot, like how Tobi got Hashriama's cells, how he got the rinnegan. Also, why would Tobi agree to keep Sasuke alive when he and Itachi slaughtered the uchiha clan?

And to answer your question about Tobi not knowing about Danzo's abilities, its because Tobi (or future sasuke) never had that same fight with Danzo. Something happened differently in the past. The Uchiha clan probably never got slaughtered in future sasuke's time, because Tobi is the one who came to Itachi remember?