I kind of forgot about that? I would personally have to re-read a couple scenes in Naruto to form an opinion on if I believe this might happen or not. But I think I will just wait and see I don't expect it will. I think the 9-tails has replenished his sealed part by now naturally. Since it was not a body part and just Chakra? Also we only saw some things escape from the body of the shinigami I'm not even totally sure if the rest got out. Or even found the way back to there original source if they had an original source.
And yes Itachi was amazing... I still hate certain things about Itachi but he's basically the only Uchiha I have ever liked, and hes not completely guided by Emo powers.
And
I think your mostly right, however if Kishimoto is smart the 4th may be able to shed some light on the Uzumaki Clan since he seems to know all about there abilities and the 4th is also smart and grew up basically married to Kushina Uzumaki there is a good chance he knows more about how and why the Uzumaki clan was destroyed, probably more than Oro would even know. So that's one thing he could share information on. And I hope the Uzumaki clan's destruction was a more important event in this series. Like maybe Madara/Obito did it in order to have less resistance in the future when gathering the tailed beasts and summoning the juubi. After all the Uzumaki might be the most powerful in the whole series when dealing with the tailed beasts.
So I hope that we learn more about that event, and also learn that it was a well planned strategy to murder the Uzumaki and not just random happenings of war.