1. As far as I know they're still the same being
2. I'm not sure as the very final chapter wasn't one of the ones translated and Gendo only briefly appears in one
3. The Spear of Lucretius was made by Shinji out of some dirt or something like that. That's all I know about it besides Mari tossing it out into space when she goes to the Apple's Core at the end
4. No. The 9th Angel is dead and has no biological influence on Asuka. We are told from the beginning that Bardiel is still alive, which is why Toji has a prosthetic leg.
5. The serpent in Seele's emblem is symbolic of the story of the Garden of Eden. I don't believe Shinji is literally a snake but I do believe he is part of Adam.
6. Yes, Anima Kaworu says that birds have the ability to transcend time and have already left for the next world. The Seagulls in Until You Come to Me would obviously be from a part of the world that isn't corrupted, as he sees Rei near a pool of fresh water. There are also plants sprouting in the GeoFront and they encounter a cat along the tracks in one of the calendars.
7. Here's the cover illustration:
and here's the link to the translated bits from Volume 5 (under Part 3). They're just fragments and nearly incomprehensible though: https://docs.google.com/document/d/1TTN ... 4bIYZzdGFY