It makes a huge difference whether the dust speck choices add up or not. If they do, OrphanWilde's objection applies and the only path to survival is to be tortured.
If they don't, so each one of me gets one dust speck total, then dust specks for sure. All of the copies of me (whether there are one or 3^^^3 of us) are experiencing what amounts to a choice between individually being dust-specked or individually being tortured. We get what we ask for either way, and no one else is actually impacted by the choice.
There's no need to drag average utilitarianism in.
Computational theory of identity so some large number of exact copies of the same individual experiencing the same thing don't sum, they only count as once instance?
You're given the option to torture everyone in the universe, or inflict a dust speck on everyone in the universe. Either you are the only one in the universe, or there are 3^^^3 perfect copies of you (far enough apart that you will never meet.) In the latter case, all copies of you are chosen, and all make the same choice. (Edit: if they choose specks, each person gets one dust speck. This was not meant to be ambiguous.)
As it happens, a perfect and truthful predictor has declared that you will choose torture iff you are alone.
What do you do?
How does your answer change if the predictor made the copies of you conditional on their prediction?
How does your answer change if, in addition to that, you're told you are the original?