Assuming the quotes are accurate, how credible are such statements extracted from a terrorist while being tortured?
Well in this instance, it wouldn't be WHILE he was being tortured, it would be well after the fact. Once a captive is broken of their will to resist is when they start talking. Of course, even then, you can't REALLY trust what he's saying unless it's verified independently. You also have to take into consideration that it's an interrogator telling this story, essentially justifying their actions which many people condemn. In short, could be legit, could be bogus.
I think they have a make-out sesh afterwards, if I'm not mistaken. CIA Guidebook, p. 1: "Do whatever it takes to milk pillow talk from ur Muslim."
It's possible he's telling half truths that fit the objectives of both camps. Fundie terrorists have the reputation for wanting to be broken by enhanced interrogation or worse as some weird rationale to justify their belief and faith. KSM wants to be safe, but he also wants to provoke a deepened American engagement against the Islamists. The underlying belief behind terrorism is to destabilize public security through mass fear and panic. As security weakens, so does the public's faith in the system. Maybe his reaction was that he thought the US government was too strong or too confident to retaliate (even as he thought its people to be weak or docile), but this goes against our scorecard of having a war for almost every year in our brief existence.