One of his charges is for solicitation to murder. To me, that means this wasn't a murder committed in rage, but planned in advance. I think he planned it for Thanksgiving because of the long weekend provided time for cover-up.
I also think the break-up story is unfounded at this point. We don't have anything concrete to indicate she was going to leave with the baby. I do not think he was concerned about losing his child.
Maybe we'll learn differently, but I think PF probably made up the story about them breaking up as a way to explain why he didn't look for her.
jmo