Hmmmmmm. Interesting, but I'm not sure if I agree with you. If the terminal was all it could be from infinite universes, it would be infinitly long or infinitly clouded, because of all the information is in such a small space. Prehaps the marine is able to read the terminal that would have existed in the universes the marine already visited, this would lend some credibility to the theory.
Your statment about the marine returning to his own universe also leads to the question: How did the marine actually travel between universes??
He could take the place of the marine that was already in that universe
He could apear in that universe at a different location, replacing the marine that was already there.
OR
He could just apear and be the second marine in that universe (unlikly, otherwise tycho, the pfhor etc would get a bit suspicous)
If the marine took the place of the other marine, he should get the other's weapons, and not the ones that he brought from his universe.
If he simply replaced the other marine, he would keep his own weapons, but whoever was controling him at the time would notice that the marine suddenly disapeared and re apeared somewhere else.
And does the marine disapear from the universe he came from? If not what happens to him? So many questions...
