On the one hand, it's a really good thought - he did need some trigger to name him as a suspect.I wonder the same. His behavior is odd but I’m not getting vibes that scream guilty from him. However, I do find it interesting his stating in the interview that he called his Dad freaking out that something happened to LB and his Dad tried to reassure him she’s probably fine. Then years later he eventually names his Dad as a suspect. What happened between the switch and why?
On the other hand - his father was his boss. When he realized stuff was serious and that he's not going to be back at work in an hour, he kinda has to call him for practical reasons, the actual aim of the call was probably not emotional support (though if you're distressed, this of course comes along).