what i don't understand is why isn't madara doing anything to stop him if he is
I think he has some remnants of the Juubi's power in him similar to Gaara's case.
I think so. If Obito was beginning to overpower BZ, chances are he got access to his eyes again, including that Rinnegan in his eye. We also see that Obito has his Kamui active now.
Gaara is still able to control sand despite the 1 tail being extracted, so maybe some of the Ten Tails chakra is still inside him.
Yes....it would seem so. Either Madara is already with a counter, or Kishi is doing this to Madara so he just stands there dumbfounded._@: