I don't think there would be any benefit in conjecturing or further dissecting his interview (IMO) - his every word has already been parsed ad nauseum for over a year, to no certain conclusion.
Just my own general take on things: have more than one 'shrink' in the family, also (not surprisingly) have had more than one person with severe depression in our family history, and have observed it intimately. To me, BB comes across as someone who muses much, and opens up his thoughts in a torrent when he senses a listening ear - perhaps more than is good for him, sometimes, but he will do it anyway because it's how he's wired. The way he distances himself and 'intellectualizes' when discussing emotionally laden events (eg. The questions he asked re the murderer) reminds me of a very common tactic used consistently but unconsciously by depressed people. Clinically depressed people will almost invariably answer "I think ____" when asked how they *feel* about something. It's a defense tactic, emotionally. Their brain is in retreat (with intermittent exception) from feeling the emotions that have overwhelmed to the point of messing with their neurochemistry. So BB's launching into the theoretical questions about what type of murderer killed his wife fits--more so than the "why" question normal people have expected in here, a question which would bring up pain and loss. Depressed people can at times also appear to live in a very introspective, self-focused world--but this would be depression rather than narcissism in such a situation. To me it is somewhat cruel to label someone a narcissist if there is an established history of depression.
I bring this up not to armchair diagnose him, but to concur with what he himself has already stated publicly concerning his mental health--and to cut him some slack as he is *not* a suspect or even an offically stated POI. If I'm wrong about him, I'll be happier about that mistake than if I'd assumed the worst about him, and then someone else ended up getting charged with Missy's murder down the road.
JMO