Tegmark 4 is not related to quantum physics. Quantum physics does not give an avenue for rescue simulations; in fact, it makes them harder. As a simulationist, you can somewhat salvage traditional notions of fear if you retreat into a full-on absurdist framework where the point of your existence is to give a good showing to the simulating universes; alternately, risk avoidance is a good Schelling point for a high score. Furthermore, no matter how much utility you will be able to attain in Simulationist Heaven, this is your single shot to attain utility on Earth, and you shouldn't waste it. It does take the sting off death though, and may well be maladaptive in that sense. That said - it seems plausible a lot of simulating universes would end up with a "don't rescue suicides" policy, purely out of a TDT desire to avoid the infinite-suicidal-regress loop. I am continuously amused how catholic this cosmology ends up by sheer logic.

Perhaps you shouldn't. That said, it is recommended by Eliezer Yudkowsky, and his words often weigh quite heavily here. I don't necessarily agree that lacking experimental verifiability means that we shouldn't take something into account when making decisions, if we have enough reasons to think that it's true nevertheless.