Someone needs to watch "Knock at the Cabin" by Shyamalan.

In practice we all know what we would do. Given that morality is at best invented and aspirational that is the moral action. Or at least we think that it is.

So, who do we torture?

It's a mis framing of the problem. In your exploration of hypothetical morality, the entity creating this scenario where the world is at stake unless someone is tortured is the one with moral responsibility for the outcome

I think it's a harder problem when you're the one that has to do the torturing. It's easier to say "yeah that dude should get tortured" than to do the waterboarding yourself. Unless you're fucked in the head of course.