Shakaku is his real name the sage said it. To answer your question, yes it is because Gaara is still alive. Tobi needs the jinjurijiki's body to bind the beast chakra to. Since he doesn't have Gaara than he can't. Also he can only make 6th paths (like the 6 paths of pain) so either way one or more of the other tailed beast would always get excluded. It's a shame I thought Shakaku was funny in part 1, I wonder if he was jealous of everyone hanging out, whilst he sat in the statue by himself
