I thought it was an interesting idea you started there. Couldn't resist putting in a bit.
I am curious about one thing. Do you think the aliens warnings against eating anything not native to earth would be absolute? Seems to me that organic matter is organic matter, is it not? I'm sure there would be things that are poisinous to humans, but that's true even on earth. Perhaps someone could explore that idea a bit. Would make the prospect of a trans-continental journey within years instead of generations a bit more plausible.