Maybe his acting has improved since Angel or maybe DB was just emotionally flat because he thought that would be represent the character. But in this episode he displayed a nice range of emotion, especially when he got the finger in the mail. It wasn't melodramatic, but his anxiety was clear. His anger, his need to get the boy balanced against the need to stay calm enough to be efficient was very compelling. It was a little insulting of Brennan to ask him why he knew she was going to help him find the killer, because the killer made Brennan mad? He wasn't acting mad. He wasn't engaging in threats or histrionics. He was concerned for the boy, but determined, not vengeful and there was no reason for her to treat him like a hysterical gal.
That kid of his looked too old for a car seat, especially back then. Today I think kids have to stay in a car seat until they're 7 or something, but back then they didn't.
He asks Brennan doesn't she think his son's mother not marrying him would be a sensitive subject. Uh. . . why? She rejected him, but that was at least 4 years ago. I don't know why his having a son is something he doesn't want to talk about and even the fact that he doesn't see his son like he wants is something that hurts, but should hurt less than it did right after the kid was born. I don't understand why they think this is such a painful, personal matter that's supposed to make our hearts bleed a little for Booth every time it's brought up.
The way Brennan said very forcefully that she wasn't going to have kids and wouldn't change her mind is almost as if the writers expected her to get pregnant some time during the show's run all along and wanted to use those words against her some day. But I don't think they actually plan that far ahead. Especially not this early on in the show's run when they had no assurance that they would even be picked up for 55 future seasons.