Pretty good dude... in regards to your question about how they can defeat Obito, there are a few reasons... firstly Senjutsu chakra is enhancing the whole thing, Kurama is willingly helping while it wasn't with Madara and the tailed beasts are far more effective when in a Jinchūriki as they can are too mindless without one. That and Obito had a random flashback which caused him to drift off.
I dunno, it makes enough sense to me, even if it is pretty over-the-top. It's always harder to get something to work right when you have to force it to do so. That and Kishimoto apparently decided that sage power > whatever Obito is using. Madara never had access to sage power at all, so his version would naturally have been weaker.
Does make me wonder what in the heck sage power is supposed to consist of, anyway. What is it, like... "the unified energy of nature" or something like that? I bet he never properly explains it in the end. >_>