Thank you! I suppose there was more info I could have shared about the Dead World, after seeing this. I can definitely understand the fact that you see Cosmere influences in the worldbuilding. A fair amount of it wasn't exactly intentional, It's a problem I've noticed myself with a lot of my stories. I think it may come from only reading Cosmere for the past few years...
There is a very hard border between the Shattered Skies, and the Dead World. The Dead world is much more stable, islands there are much larger and move very slowly. In the Shattered Skies, hunters and foragers use grapple devices that (again,) connect to the Galeshards for a firmer grip. These can usually be powered by traces of some other powers I haven't mentioned, which mainly come from worlds above the Shattered Skies (Unknown to anybody living on the Shattered Skies.) I won't go into too much detail, mainly because I don't have much more defined detail than that.
About your thought experiment, there are no currently living people of the Dead World. During the events of the story, it will become clear that there were, once, but something killed them off.
Side note: People that live in the Shattered Skies are called Avarians. I figure it would be more convenient to write than "People that live in the Shattered Skies" or something similar.
When it comes to Flora and Fauna, I made a critical mistake in Draft 1. Namely, forgetting it completely. The only animal life other than the Avarians in the story are Dragons, and 2 species found in the Dead World. (It's got Dead in the name, but it has more animal life than the Shattered Skies...)
The world was Shattered, mostly. The entire planet split apart, however, the power that resulted in the blast only got so far deep, leaving a main planet beneath the Dead World, with a very rough jagged surface. This is yet another World that the Avarians don't know about.
You are correct to guess that there is fog between the Shattered Skies and the Dead World. The Dead World is typically described as having a hazy, foggy grey sky, as it is in the middle of a large fog that surrounds the Dead World and the world below it. Crystal Shenanigans wouldn't quite work the same in the Dead World, as the Shattered Skies were a bit of a unique case. I won't say too much more for now, though I may talk about the Dead World in a later post, when I've revised it for Draft 2. Currently, I'm working on life in the Shattered Skies though.