1 - Why is it, Vivec is suddenly so week after the destruction of Lorkhan's heart? I understand he stole false-divinity and God-like power from it, however, did he not have God-like power already due to have successfully reaching CHIM?
If Azura was sort-of afraid or cautious of Vivec due to his equal footing with her, why is he so week when you meet him in Morrowind?
Those examples make no sense, specially if CHIM is so great that it could give power over time itself. . .
And Two, Did Dagoth Ur kill Nerevar or did the Tribunal? I believe it was the Tribunal. However there are just so many accounts as to what had happened back then.
Two disclaimers: I'm late in reading this (sorry) and I haven't read in-Skyrim books yet, but I was there with Vivec...
Say what you will, but Vivec's power came from Lorkhan's heart. He was not a god before that. I'm not a believer in Chim (at least, not the altered definition that gets attention in these forums), but Vivec certinanly had style. That's all I'll give him credit for.
Azura's feelings towards Vivec were complex, but he was powerful. If he could displace her in the beliefs of the masses, then that'd hurt Azura (but not destroy her), but remember - - and here we go - - Azura was a true god. Vivec was a very powerful mage and immortal all because of the heart. Argue about what a God really is, but take away the source of his power and Vivec was at the mercy of the Nerevarine pretty quickly.
(Note: Remember that Azura has been waiting a long time for revenge against the tribunal. She didn't hope it'd come some day - she knew it would. That "not if, but when" proved to me she was a real god. (Take away all faith and would it hurt her? you ask. hmmm. idk.)
Dagoth Ur's role was very muddled and I never really knew. One thing was certain, everyone was lying about something. In the end it didn't matter. Dagoth Ur's actions bent towards the evil end of the spectrum and he needed to go. (The same happened to Almalexia, if you recall. Although, "crazy" could also be used to describe her at the end.) You are defined by your actions. Do bad things and you are seen, rightfully so, as a bad person.
War_Psyence said Nerevar was was religious; he was Azura's pet. Not a flattering statement, but very true. You have to wonder what Nerevar or even the Nerevarine would have done if they were more selfish and didn't listen to Azura.