Bino,
I know you think his nonchalance is a point in his favor...I see it as the opposite. As cindy said, it's a tool of manipulation. He has a history of lying to her about contact with women, and one of the consequences of that is that in the future the burden of proof is on him, not her. In his shoes, were I innocent, I would have moved heaven and earth to prove my innocence. Not gone to bed at 8 and said, "you should just trust me." If I were innocent, I would have been sick to my stomach at the thought of my spouse sitting up all night trying to "just trust me."
No, I would have been right there with her, staying up all night trying to come up with answers.