I'd like a little stronger of a connection between the Nhaama desert and the Burn before we conclude they're related, but it's a theory.

It actually kinda blew my mind to go back and realize that "Othard is where Solus first saw the destructive power of the primals." didn't necessarily mean that he actually saw actual primals actually destroying things. It never sat right with me that the Echo sounded just after Silvertear Skies and just before the first Eorzean appearance of the primals if they'd been on Othard prior. Why didn't the Echo sound then? Wasn't the era already collapsing? Doesn't the aether necessarily have to be imbalanced on a massive scale for primals to exist (according to Minfilia)? This might be a retcon ... but it's certainly one way to make things smoother, if it's the case.

Also, I agree about Zodiark and the moon. If the living, growing physical world has Hydaelyn "transdimensionally inside of it", and She "expelled" Zodiark, it makes sense to assume that the moon is a dead body with Him transdimensionally inside of it, but since it's not a way to "the sea" (aetherial realm) but to a rift-prison of some kind, the moon is "dead'. Though Hydaelyn claims that the division itself predates Life ("as we know it"), which may itself be part of Her defense.

Recall the hints in the Chrysalis. An aetherial rift (pocket dimension) whereby the only things that exist are quasi-formed Dark-aspected crystal structures each Ascian's "place" around Zodiark, and a door symbolizing that exists outside of the world we know - you have to get there through another way.