So Chaos, on the issue of Breath, your stance is "only Nalthis people have it, but other planets may have it similar"? I guess I can stand by that.
I think that souls are extremely powerful. Each intelligence (and human) has something special and unique about them. This uniqueness and this intelligence (which apparently, according to HoA, stays with us after death) is our soul. Breath is a piece of this soul, specifically, the part that holds the lifesense, perception for color, and perception for music, etc. When you have more of it, it allows you to strengthen your body (immunity) and your perceptions (color, sounds).
So I think that in order to have humans (as we know them), they must be intelligent.
If they are intelligent, they must have a Breath.
Therefore, everyone has a Breath.
Now, I do think that Endowment does make it (either directly or indirectly) possible to give that Breath away, which is unique to Nalthis. But I think that intelligence (that seems to be granted by Shards or possibly Adonalsium) innately holds a Breath. So maybe you're right. The Breath could be of Endowment. But I think that the people on Scadrial have one too, of Preservation. They just can't use it.
Ooh. Except maybe... instead of allomancy genes, they have breath genes. Except that doesn't work. The ordinary people of Nalthis are comparable to Scadrial. Although maybe instead of allomancy genes, it is the ability to give away breath genes. That work.
Also, on your Vo theory: I love it when you read my mind. I've thought the same for a while, but I've just never written about it. I mean, it makes sense. You have no awakeners, you come to the forest, Vo returns and suddenly, people start learning about awakening.
Ooh! That gives me an idea. What if, the reason why Endowment couldn't help them before is because there wasn't enough color? I mean, Hallendren is not only the awakening capital of the world- it's also the dye capital of the world. Perhaps there is something special about the tears of Edgli.