We could put the theories at the very bottom of the Main game page, with some kind of spoiler tag maybe ? I think it'd be the only place where they could fit, since they wouldn't go well in the Gallery or Walkthrough categories, and having spoilers in the middle of a presentation article would be weird, except if we're able to get a Spoiler Template that would hide the text until asked otherwise by the user. Like a spoiler tag accompanied by the "Show" clickable text, which would display the theories. Then the "Show" text would become "Hide", so the text can be hidden again for convenience. Then again, we might already have that and I'm just not aware of it.
As for the rest, I'll get to learning grids on wikia editing and I'll be good to start reediting this page !