I agree with most of this but all that adaptation and behavioral complexity could also happen to a race of p-zombies. And I still struggle to see how "I" (as distinct from behavioral patterns mostly indistinguishable from "I"-hood) can emerge in a materialist univere without some substrate that has properties beyond the mechanical.

I'm veering dangerously close to mysticism and the non-falsifiable here. But it seems inescapable for the same reason Descartes clearly stated. My "I"-ness is the only indisputable fact about reality and the one from which all other beliefs follow.