I disagree with your conclusion. Specifically, I disagree that

This is, literally, infinitely more parsimonious than the many worlds theory

You're reasoning isn't tight enough to have confidence answering questions like these. Specifically,

• What do you mean by "simpler"?
• Specifically how does physics "take into account the entire state of the universe"?

In order to actually say anything like the second that's consistent with observations, I expect your physical laws become much less simple (re: Bell's theorem implying non-locality, maybe, see Scott Aaronson's blog.)

A basic error you're making is equating simplicity of physical laws with small ontology. For instance, Google just told me there's ~10^80 atoms in the observable universe (+- a few orders of magnitude), but this is no blow against the atomic theory of matter. You can formalize this interplay via "minimum message length" for a finite, fully described system; check Wikipedia for details.

Even though MWI implies a large ontology, it's just a certain naive interpretation of our current local description of quantum mechanics. It's hard to see how there could be a global description that is simpler, though I'd be interested to see one. (Here local/global mean "dependent on things nearby" vs "dependent on things far away", which of course is assuming that ontology.)

With all kindness, the strength of your conclusion is far out of scope with the argument you've made. The linked paper looks like nonsense to me. I would recommend studying some basic textbook math and physics if you're truly interested in this subject, although be prepared for a long and humbling journey.