A lot this seems fairly arbitrary, though that may be due to the wording. I suppose I don't really agree with they way absolutes like "impossible" and "100%" are used.
In regards to the multiverse theory, I'm gonna rephrase it to say that basically there are an infinite number of universes with an infinite number of possibilities. However, infinite possibility does not mean all possibility. Given an infinite number of chances, the probability of something not happening may draw near zero, but it never reaches zero. Basically, even with an infinite number of chances, it is not absolutely guaranteed that Aloria exists. It's quite possible that you could literally (haha) search forever and never find Aloria.
The 1,000,000,000 larger universe theory feels a bit more… hmm. At first it seemed incredibly farfetched to me, but that thought in itself was based on some assumptions. I felt this way since an exact copy of Earth would have meant that everything, from the cosmic level to the subatomic, would have had to happen exactly as it did here. For example, this clone Earth would have had to have the same galaxy formations that gave rise to the same Milky Way galaxy that gave rise to the same constellation of stars that gave rise to the same Solar system and the same Earth which gave life to the same organisms which grew into the same Aristotle or the same Galileo who would have had to see the same stars and made the same choices to move history in the same exact way as it did on this Earth to give rise to an exact copy.
Basically a clone of Earth would have meant not just a planet, but another entire ~13-billion-lightyears-radius of the universe that would have to be an exact repetition of our own ~13-billion-lightyears-radius observable universe. That is what seemed farfetched to me. But then, on further thought, why not? But I digress as I feel the bigger universe theory can be countered with the same argument as the multiverse theory.
Personally, I believe that fictional universes exist in a metaphysical sense. Do things necessarily have to be physical to be considered real? I like to think that everytime someone imagines a world and fleshes it out, they are essentially creating a pocket universe within their mind.