By "the preface" do you mean the "memetic hazard warnings"?

Yes.

I don't think that is claiming that it is a rational response to claims about the word.

I don't get this. I see a very straightforward claim that cryonics is a rational response. What do you mean?

This is a quantum immortality argument. If you actually believe in quantum immortality, you have bigger problems. Here is Eliezer offering cryonics as a solution to those, too.

I've read that as well. It's the same argument, essentially (quantum immortality doesn't actually have much to do with MWI in particular). Basically, Eliezer is saying that quantum immortality is probably true, it could be very bad, and we should sign up for cryonics as a precaution.