You're right again, thanks again :-) I was indeed using a sort of quantum suicide assumption because I don't understand why I should care about losing candy bars in the worlds where I'm dead. In such worlds it makes more sense to care only about external goals like saving weasels, or not getting your relatives upset over your premature quantum suicide, etc.
Specifically, I think the middle part of the argument would fail, because you'd go, "eh, if they're executing half of my future selves, I can only save half the weasels at a given cost in average candy bars, so I'll spend more of the money on candy bars".
Imagine you're playing Russian roulette. Case 1: a six-shooter contains four bullets, and you're asked how much you'll pay to remove one of them. Case 2: a six-shooter contains two bullets, and you're asked how much you'll pay to remove both of them. Steven Landsburg describes an argument by Richard Zeckhauser and Richard Jeffrey saying you should pay the same amount in both cases, provided that you don't have heirs and all your remaining money magically disappears when you die. What do you think?