The first rule of a con is: don't let the mark think too long about things. I'm pretty sure Harry is being conned, but I don't know by whom. That said, I have some thoughts on the matter.
First: Although several people 'know' Justine is pregnant, we never actually see evidence of a pregnancy. Harry makes some vague quip about an aura, but he never actually uses the Sight. You'd think he'd jump at the chance to see his niece-or-nephew with the Sight when the niece-or-nephew is still in the process of being formed: you want to talk about magic, that's potent stuff right there. And, come to think of it, literally nobody else saw any evidence, either. The people who know, know only because Thomas or Justine told them. Prediction: Justine's not pregnant, but Thomas certainly thought she was. Why? Because it made him much easier to manipulate into doing something recklessly stupid and foolish and inexplicable.
Second: Did I mention Thomas's attempted assassination is recklessly stupid and foolish and inexplicable? What if the entire point of the attempted assassination isn't to kill anyone, but to create chaos that forces Harry to do terrible damage to his own alliances? Look, e.g., at what Harry did to his relationship with Ebenezar. Look at how he almost wrecked his frenemy status with Lara. Look at...
Third: The Titan is a hell of a distraction, isn't she? She's taking up all of Harry's attention right now, isn't she?
Fourth: What if there was a bad guy so powerful, so subtle, so over-the-top, that this bad guy would be willing to orchestrate a Titan attacking Chicago just to ensure Harry was going to be too distracted to notice what was happening around him?
Fifth: Don't we already have a bad guy like that? Namely, Nemesis?
Sixth: Isn't it kind of interesting that Thomas isn't able to say anything clearly? Harry just assumes he's saying 'Justine' and asking Harry to look after her. What if Thomas is saying 'Justine' because he's trying to warn Harry?
Seventh: Nemesis has infected Justine. Nemtine then manipulated Thomas into doing something so reckless it would force Thomas's number one ally, Harry, into a series of reckless and potentially alliance-wrecking moves in order to save him. The Titan's arrival is both a feint and an attack all at once: if Harry wrecks his alliances, the Titan will make short work of him. If Harry keeps them, the Titan will keep him busy for long enough so that Nemesis can advance its own agenda.
Eighth: But wait, Justine's a mortal. Isn't there something about mortals and free will, and whenever that's threatened by forces-from-beyond Uriel gets off the bench?
Ninth: What if Uriel has already come off the bench and Harry is his unknowing agent? What if Uriel saw this coming, and thus ensured Harry would have the placard and the Spear of Longinus and two Knights of the Cross on-call?
Tenth: I'm thinking virtually all the action in Peace Talks is a shell game, it's three-card monty, meant to distract the readers from what's really going on.
Discuss! :)