EDIT: It occurred to me people might not want to follow the links, so the TL:DR version of the question is this: "Realistically, how thick would this have to be to be habitable, farmable and stable enough to hold up cities?"
I asked the question originally here:
I deleted it based on feedback.
I also asked in on the worldbuilding beta here:
I edited the question down when I realized it was too broad but it still got closed.
Is there a way I can ask the question on stack exchange? If so, what site would you recommend?
Also note this question on SF&F Meta: https://scifi.meta.stackexchange.com/questions/8028/when-is-science-fiction-existing
Some good back and forth in the comments, but the gist I get is that they don't want any non-published materials discussed there. So here I am, hoping to not get dumped on by yet another community. Any help would be greatly appreciated.