First, I'm relatively sure that man is born of Nirn, not Aetherius, and as such will not be freed to godhood by its unraveling, but annihilated utterly. If it isn't true, it seems more likely still the Altmer believe it to be so.
Its truth is up in the air, but the Altmer certainly don't believe it. All their myths state that Man & Mer are both descended from the Aedra.
I doubt it. Everything we've seen so far suggests that the Altmer ideas of everyone being a depowered Aedric spirit are full of crap. Even Boethiah went out of his/her way to expose the old Aldmeri ideas for the BS that they are, causing a mass exodus. Alduin and Kagrenac showed that the reversal of creation is not turning yourself back into a god, it's your very soul getting consumed to empower the Divine.
1st: I have no idea what you're talking about with Alduin.
2nd: Boethiah just claimed that (at least some of) the mortals on Nirn were depowered versions of / descended from spirits more like the Daedra than the Aedra. The dunmeri word daedra means "our better, stronger ancestors." Also, she's the prince of lies.
3rd: Kagrenac believed in a variant of the depowered Aedric Spirit theory, in which mortals are subgradients of a subgradient of a ... until you hit something way more awesome than the Aedra. He also ended up being so much golden shine on the skin of an intially battery-less robot.
4th: The fact that other cultures have slightly different beliefs from the Altmer is hardly evidence against their beliefs. You might as well have brought up the Cyrodiilic beliefs, which actually contradict the Altmeri beliefs.
5th: Everything we hear about ghosts supports the Altmeri view, from what I see. When not tied down to a mortal shell, your soul is A) immortal, and
effin' hates the mundus. That's the closest we can get to having any evidence, and it certainly doesn't prove the Altmer wrong.
What if I don't like that kind of godhood?
Same thing that happened if you didn't want mortality.
The heroes of Sovngarde refer to you (indirectly) as "mortal". They're suggesting your wimpy non-immortal ass is why Shor has to hide. That suggests that the Nordic heroes there are immortal spirits. Not much of a difference between them and most Daedra anymore.
Not all Lorkhanic methods of ascension are CHIM.
I think you're reading a bit to much into the "mortal" line re: Shor's appearance, but the simple fact that ancient heroes from the mythic age are still walking around in Sovngarde makes the point that the spirits there are immortal well enough. I'm not 100% sure if you're trying to make some other, more aggressive point there, but as it stands I think I agree with what you're saying here.