"What if we could erect a future of love and harmony on the everlasting pain of someone who had himself committed mass murder, who had tortured those children? (...) And more urgently: what if the person whose genitals are crushed and skin is being burnt knows the whereabouts of a bomb that is about to explode and kill millions? Would we answer: yes, I do consent? That under certain very limited circumstances, torture is acceptable?"
And I don't think there is an easy reply for this.
I appreciate your posting this long discussion of important issues. However, I think there is a very easy reply for this. It is that we don't live in a universe where torture has or could have any of these effects. Torture does not give us access to the truth - the history of witch hunting tells us that much. Torture could not deliver utopia.
It is a false moral dilemma to imagine that we could achieve worthwile ends by committing torture, and it is self indulgent (in my opinion) to imagine that only our high moral standards restrain us. In fact torture is a dead end, in every sense of the world.
(EDIT - my point here is not that in fact torture has never delivered good, but that it is inherent in the design of our species and the universe that it could not)