The original problem is that you either torture one person or give 3^^^^^3 people dust specks. For purposes of this thought experiment, therefore, we must assume that there exist at least 3^^^^^^3 people in some number of universes.

3^^^^^^3? Do you know the difference between 3^^^^^^3 and 3^^^^^3? Compare the size of an electron and the size of the entire universe. Then forget that because that doesn't come close to demonstrating it. This means that the fact that you said the original problem is about 3^^^^^3 when it is actually about a mere 3^^^3 is a relatively minor error.

That you are so willing to jump from 3^^^3 to 3^^^^^^3 in the same conversation suggest you don't really grasp the point here. The amount of people experiencing discomfort really does make a difference. There is an unimaginable amount of pain at stake.