The "Mild Boar and Jungle Mammoth are just what the person from the Harsh Survivalist Ice Village calls pigs and elephants" speculation is hilarious and I wish I'd done that on purpose; I hereby retroactively declare it canon.
One roll for all universes.
Regarding PCs & NPCs: My plan for handling the NPCs is pretty much as you said; if I end up needing multiple worlds, I'll make sure the human players are distributed as close to evenly as possible.
Regarding the premise: Being better at interdimensional travel than at regular teleportation produces some weird incentives. Also, magic-users are generally understood to be crazy; "that mage is doing something unusual!" is about as concerning as "that fire is hot!"
Thanks, yes, you're completely right; I wrote this for an older version of the scenario and forgot to change it. Edited now.
Your theory is correct. I had some sort of clever justification for why that made sense in-universe but I forget what it was; the Doylist reason was that I wanted the red herring in this puzzle to be as simple as possible.
The original generation code is up here if you want to take a look.
(Good question, by the way; I added a note to the main post to clarify this.)
Yes to the first question.
To the second: you can aim to reduce repair costs with your interventions, but since they won't come out of your budget that's more of an optional extra for further impressing the brass.
That's exactly right.