Chapter 527 answered the questions
you know what i liked about this chapter??
it solves the madara/tobi mystery for me!!
i never believed he was real madara until now......why, because the shell of his former self thing (i thought that there was no way for his mind and body to act without a soul)
but thats obviously not the case as chap. 527 proved that cuz samui,atsui and darui were still concious.....
so.....to me that means madara is tobi-tobi is madara
and madara's soul is somehow trapped in the pure world....(some awesome 1st hokage sealing tech. or sumthin prob. the cause of this.......he danm sure wasn't beatin with wood no jutsu and is seen with huge scroll in his famous panel vs madara)
this is why madara needed nagato to use gedo on him!!!!!
and yes this also explains the 6th coffin.......if his soul is trapped in the pure world them kabuto would have the capability of summoning him......even tho he still existed........according to the rules of edo-tensai as we currently know them
and since madara is only a shell of his former self and edo summons come back with powers fully in tact, the edo would technically be stronger.......but madara still has his own advantage as he knows his self better than anyone
that would explain their reluctancy to fight one another and madara's reaction
so to wrap it up.......
madara is madara....tobi is madara
and sixth coffin is madara