A multiverse isn't impossible, but verifying it would be a job for psychics, not physicists.

There's a really good hint at what dark matter really is. The bigger the scale, the greater percentage of the matter is said to be "dark" - which means they don't know, actually, no serious physicist claims its real. If the proportion increases with the scale, the problem can't be what you're looking at. Its an error at the smallest level.