Zapata

I think you could have a near-constant low-tone pulse whenever the viewpoint is in Luthadel that swells when a character uses emotional Allomancy, which also works because of the Lord Ruler's soothing stations and soothing aura. It foreshadows that reveal.

It's just a combination of parts of the terms "full feruchemist" and "mistborn", although you're right about the impression it lends. Chances are any fullborn-like beings we see in the future will not actually be born with all the powers (and neither was any past fullborn).

As far as oaths go, you basically just need to be able to say the First Ideal, then be lying to yourself about four things. Not hard. And maybe be creative in some way.

Even if you are really bad at predicting someone's responses, odds are your target would think something is wrong with themself emotionally before they suspect you of being the world's only allomancer. However, I definitely think that out of zinc/brass and pewter, no one either wants to emotionally manipulate people or admit to wanting it, so pewter comes out as the preferred allomantic metal. We have virtually no reason to pewter drag, so there is little risk of savantism in real life. It has no other downsides and is not immediately noticeable like iron/steel or cadmium/bendalloy, and isn't useless (in real life) like aluminum/duralumin/nicrosil/chromium/copper/bronze. Gold and electrum are situational at best in real life, and I don't think anyone really prefers them. Tin is the only comparable metal, imo. But the real-world choice probably has to be between tin, pewter, zinc, brass, cadmium, bendalloy, and maybe gold and electrum. And out of those, I'd prefer pewter

I thought of this as well, although I think you put it into words better than I would have. The first Divine Attribute also draws the spren in the first place, I would add. One other thing though, is that following Shallan's arc, I think that the Lightweaver Truths also follow the direction, commitment, nuance, incarnation pattern guided by the divine attributes. Not necessarily in their character, but in their effects on Shallan. The Truth progression is that her first truth solidified her bond to Pattern (maybe), her second showed her commitment to the Truths, and her third (where she reintegrated Veil) showed nuance by not having her integrate Radiant. Furthermore, Cryptics are naturally drawn to people who lie to themselves (Creative), and the Truths help the Lightweaver embrace honesty.

This is probably true. For someone without a photographic memory or intense memory training, the most use a coppermind would get is probably to store the contents of a textbook chapter into the coppermind, then tap while taking a test. And for most people, this would be a one-time use memory. I kind of doubt that most people could keep a library or even a book's worth of content in a coppermind forever the way Keepers do.

We know that humans as a whole feel their emotions more strongly than singers do, since singers rarely draw spren. This is what frustrated Listener scholars who tried to attain more forms in the Eshonai/Venli viewpoints. So already this appeals more to the spren. I believe that the Dawnsingers would take True Spren into their gemhearts and attain forms of power that granted one surge each. (This is why the Heavenly Ones betrayed Lezian and Raboniel during the battle; they all have personalities that would draw Honorspren, and so would not hurt defenseless people) This would also be why the Fused believe that Adhesion is not a true Surge; because "Adhesionform" would only be granted by Bondsmith Spren, and they did not ever enter a gemheart. Perhaps human bonds were more attractive than Dawnsinger bonds because humans don't have gemhearts. Humans arrive and start to draw emotion spren and True spren more readily than the Dawnsingers do, and they begin expansion out of Shinovar. The Dawnsingers approach Odium in order to stop the humans' expansion. Either this drives the spren out of Dawnsinger gemhearts, and Odium reconnects them with their previous Surge by turning them into Fused, or Odium corrupts the spren in their gemhearts to Fuse the Singer and spren. Whatever Odium does drives all True Spren away from the singers until Eshonai bonds Timbre.

Except I'm not so sure the Skybreaker oaths do that. The second one is intended to be about following the law, (Szeth's was not though) the Third Ideal is about following a code of the Radiant's choice, and the Fourth Ideal is about completing a just quest of the Radiant's choice. The Fifth, which is about actually becoming the Law (which I believe is about having the confidence to create justice yourself). Essentially, each Ideal trains the Skybreaker to have the Confidence to create Justice themself, rather than seeking it elsewhere

Aether of Night spoilers:

That's how MeLaan healed Marasi that time in Bands. The real question is what Ulaam's healing concoctions are. Forton's potions, perhaps? Or liquid kandra juice?

That could make sense if Re-Shephir was a Core Aether. The question of who released Midnight Essense would just be a question of who sought her out and bonded a corrupted Midnight Aether. Additionally, this aligns with Aesudan's "Radiants". If Yelig-Nar is some kind of Roseite Core Aether, it could have distributed buds to the Queen's Guard, and to Aesudan and Amaram (assuming the crystal isn't literally Yelig-Nar).

to add to this, the Terris people have begun a project to breed a Full Feruchemist, which reduces the mixing between allomancer and feruchemist bloodlines. I think that we readers have come to overestimate the prevalence of twinborn because we see three in AoL (and Forch later on).

The Sleepless seem to disagree on whether Dalinar is the destroyer. To me, it seems like this could be a misdirection. But even if it holds true, it says nothing about the redeemer.

Still, something would have to happen to make the Oathgates dangerous/inaccessible. Sja-Anat Enlightenment, total destruction, or maybe the Radiants just ended travel through the CR again.