You have to include the presumption that there is a quantum variable that conditions the skull card, and there is a question about whether a non-quantum event strongly conditioned on a quantum event counts for quantum immortality ... but assume Omega can do this.

Neither the problem itself nor this response need make any mention of quantum immortality. Given an understanding of many-worlds 'belief in quantum immortality' is just a statement about preferences given a certain type of scenario. There isn't some kind of special phenomenon involved, just a matter of choosing what sort of preferences you have over future branches.

That any agent, even an arbitrarily powerful one, is willing to bet an arbitrarily large number of doublings of my utility against quantum immortality is phenomenal evidence against it. Phenomenal.

No, no, no! Apart from being completely capricious with essentially arbitrary motivations they aren't betting against quantum immortality. They are betting a chance of killing someone against a chance of making ridiculous changes to the universe. QI just doesn't play a part in their payoffs at all.