It's naive to believe the FSB (or others) wouldn't use him however they wanted. Snowden has absolutely zero leverage. He can be deported to the US at any time, and Putin has proven he isn't above killing virtually anyone, no matter the public profile.

And I remember that fake Q&A session with Putin were Snowden asked a question about surveillance of their own people and Putin basically said that the Russian state would never ever do such a horrible thing. It's almost funny.