1. Landfall was the return of Numidium, its time-shattering abilities rendering Akatosh useless/powerless. It cracked Nirn to pieces because... perhaps it hated the Aurbis that gave birth to it? The Numidium was activated by the racial sacrifice of the Dwemer, correct? I recall some discussions bringing up the possibility that the Dwemer were well aware of the structure of the Aurbis, that it was the dream of the Amaranth (Anu/Godhead, it matters not how many "levels" of the Aurbis they knew existed), and that they wanted to use their technologies to escape this reality for a more "pure" one, or at least one that didn't confine their race to the dream of another entity. However the Dwemer understood the structure of the universe only in the sense an academic would, and could not comprehend or fathom the ways in which one could achieve Amaranth to conquer the dreamscape. Their construction of Numidium created an anit-temporal battle-bot with a hatred of the Wheel but no way to leave it. Numidium returned and shattered Nirn, the "hub of the Wheel," perhaps as a last ditch effort to undo the Wheel and end all existence, and with it, its hatred for it.
2. Destroying the Hub of the Wheel did not end the dream. Something held it into place, described as "forces unknown." The cogs and the wheels could mean many things. Perhaps ALMSIVI saved the day, and the cogs and wheels are Sotha-Sil's doing. Perhaps they are the work of other entities, one can only speculate. Perhaps the dreamer himself (Anu) held the hub in place, not permitting his own dream to end (he is in a sensory deprived coma after all, if the scriptures of the sermons are to be believed. And one in a coma cannot wake).
3. Not all of the species from Nirn made it to the moon to escape Landfall. The Khajiit "were there first," undoubtedly due to the high reverence held for the moon in their religious beliefs and practices back on Nirn (as can be read about in the games). They must have perfected some magic allowing travel to the moon long before Landfall occurred. The Dunmer followed them. I doubt that any of the races of Man or the Argonians are there. The only thing related to Argonians that we hear about is the Hist, and the Hist seemed to be connected in some way to the Digitals. So...
4. Either the other races perished on Nirn or fled Nirn for some other plane. The Digitals could be the TEM (Third Empire Man) living either outside of Anu's dream in the 12 worlds of creation or in memory only.... I find the latter conclusion more possible. Memory, which possesses the collective experiences, events, feelings, emotions, and happenings of everything that has ever occurred, is reluctant to let go of the idea that the Empire of Man no longer exists and there is no way of bringing it back. Its been obliterated by Numidium. Memory keeps plucking its ghostly fingers into the world, but is unable to make any sort of coherent sense, because its a mash-up of memories from bygone eras when things were different. It is connected to Nirn, which is shattered and towered over by a time-obliterating aurbis-hating robot that refuses to let it gain a foothold. Memory probably consists of all of the deities and heroes who are doing battle with the planet-sized Numidium among the shattered fragments of Nirn. It wants to fight and win, to regain the ability to "mend" things back to the way they were (exemplified by the scene with Akatosh in the Corner Club). But it can't win. Time was broken by Numidium, which is a super-powerful robot that keeps destroying Memory's avatars... beings from the games, from the history of the TES universe, etc. All of the Aedra and Daedra are probably part of this, fighting Numidium because they want their playground, their arena back to the way it was.
5. The Dunmer on the moon are following the teachings of Vivec and ALMSIVI. They know that to give some sense of stability to the mess created by Numidium, someone needs to undergo the process of becoming the New Amaranth, who can lead the people into becoming the Nu-Men.
6. ALMSIVI has become some CHIM trio of superheroes that also works with Dagoth Ur and Molag Bal (the former of which now helps ALMSIVI out because.. well.. time broke and why the hell not?). ALMSIVI flies around doing battle with all of the chaotic elements that spawn from a universe with a broken time-scape, allowing the last remnants of anything "normal" to exist underneath the lunar surface. Any threats to this world would take away the ability for anyone or anything to achieve the new Amaranth, and so Tomorrowind must be protected at all costs. Jubal talks as if Vivec, Almalexia, and Sotha-Sil have battled a seemingly infinite amount of weird threats in a world where time and space have been distorted by a vengeful robot that tried shattering the whole universe to pieces. I also suspect that the interior of Lorkhan's corpse has something to do with allowing Tomorrowind to exist, giving the tribunal enough power to actually combat the weird things that threaten the new nation.
7. Jubal's final confrontation with Numidium does one thing that no one thought possibly: bestow the idea of Love upon Numidium, which can be likened to bestowing the idea of Love upon the Dwemer race. Numidium dies because with such a knowledge of Love, the Dwemer may have understood their ambitions a little bit better, perhaps they wouldn't have ever created Numidium in the first place. If Numidium never exists, perhaps Nirn never gets shattered, perhaps the universe as-it-is after Nirn is shattered becomes stable again, and things will never be the same? Who is to know? The erasure of the text in the last section that was the text in the beginning section suggests something about time and it being mended somehow. The restoration of Lorkhan's heart to his body? Not sure what that can mean. I have to admit the ending is thoroughly confusing me but it definitely left me with a sense of happiness, that something was finally made right in a universe where seemingly everything is out to proliferate suffering.