The way the problem reads to me, choosing dust specks means I live in a universe where 3^^^3 of me exist, and choosing torture means 1 of me exist. I prefer that more of myself exist than not, so I should choose specks in this case.

In a choice between "torture for everyone in the universe" and "specks for everyone in the universe", the negative utility of the former obviously outweighs that of the latter, so I should choose specks.

I don't see any incongruity or reason to question my beliefs? I suppose it's meant to be implied that it's other selves that exist because of the size of the universe, so there's either one of "everyone in the universe" or 3^^^3 copies of everyone, but in that case my other selves are too far outside my light-cone for "iff you are alone" to be a prediction that makes sense.