The OP was careful, it seems, to avoid that issue. (Infinite set agnosticism?)

I don't see this. I am referring particularly to this paragraph:

No, this view of reality claims that your current observer-moment is repeated infinitely many times, and looking forward in time, all possible continuations of (you,now) occur, and furthermore there is no fact of the matter about which one you will experience, because the quantum MW aspect of the multiverse has already demolished our intuitions about anticipated subjective experience.

I agree with you that the Born rules imply meaningful probabilities; but it seems to me that the OP does not believe this, at least in the part I've quoted.