That was a very nice chapter, I rated a 5.
There seems to be a confusing between the kaguya clan and the name of the princess Kaguya Ootsusuki, which are not related at all. Her family name is Ootsusuki, and her first name is Kaguya, just like her son is Bagoromo Ootsusuki.
Since the S6P's name is revealed, I think we might conclude that Rikudo is his nickname or a title.
The manga already refered the Uzumaki Clan is a branch of the senju clan, they are in fact close relatives, therefore they are also descendents of the S6P, like many others, but the Senju and the Uchiha are referred as the S6P sone's direct descendents...
People do complain a lot regarding the Hokage's monopoly in the war since they arrive. I must agree in part whit this argument, but they´re presence serves a purpose, they are here to acknowledge Naruto has the one that surpassed all of them. Remember Naruto's dream?!
I believe this chapter explains why the juubi is vulnerable to senjutsu. Since all chakra comes from the Tree, the juubi can claim it back absorbing it from the ninjas, however the natural energy/chakra it´s a different story...