"omniverse is a word wayof saying every possible universe there is inexsistance"
Almost. It is not all possible universes in existence, it's just plain all possible universes with no regard for actual existence. It specifically deals with all possible universes with all possible laws of physics, and is more of a purely conceptual thing.
If you mean to reference the multiple possible universes which would together comprise the entirety of space, time, and matter/energy, you want the word multiverse, which sounds more like what you want.
Seems like a matter of semantics now, but once you reach the point where you would deal overmuch with either concept the difference is actually sort of important.
Sounds cool, though! What experience/qualifications does your friend have?