Parallel copies of me are not me. Dying in X% of Everett branches has X% of disutility of dying.

Gradual change feels OK. Less gradual change feels less OK (unless I percieve it as an improvement). Going to sleep at night and knowing that in the morning I will feel a bit differently already makes me nervous. But it's preferable to dying. (But if I could avoid it without bad consequences, I would.) Small changes are good, because more of the future selves will be more similar to my current self.

How exactly does one measure the similarity or the change? Some parts of myself seem more important to me than other parts. Maybe if I make a matrix of how much some parts of me influence other parts of me, it would be some eigenvector. A part of me that strongly influences other parts of me, is more me. You can change my taste for ice cream and the rest of the personality remains pretty much the same, so I would be willing to sacrifice the taste for ice cream for survival or even some minor benefit of the remaining parts.

Would making 2 copies of me double my utility? Well, it depends of what "my" utility means in this context. Neither of the copies would perceive the utility of the other copy, so neither of them would feel like anything has doubled. But there would be 2 people having the utility of being alive, so globally there would be twice as much utility for my future selves, just not twice the utility for any particular self. (Just like dying in 50% of Everett branches does not mean that there is a self which feels only 50% alive.)

If I had an opportunity to copy myself, assuming that each copy will have the same quality of life as I have now, I would do it. If I would have to pay for making the copy... I don't know how much would I be willing to pay. (Also money is not exactly the same thing as utility, so if I'd have to split my property in two halves -- a half for each copy -- it would be worth it, because each copy would get more than 50% of utility.)

Without cryonics or uploading or some other immortality treatment, selves die. Pretending that you continue to live in a galaxy far far away is like pretending that you continue to live in heaven. And by the way, that's not a cheap analogy, because in Tegmark universe there exists a heaven where you will be after you die, assuming "heaven" = a place where you get 3^^^3 utility, and "you, after you die" = a particle-level copy of you in the moment of your death, except that in heaven you will survive. And this is not a good news, because hell exists too, and maybe a random afterlife is more like hell than heaven, in which case a prolonged life in our universe is preferable.