The Accords wouldn't be broken per se, but killing a wizard of the White Council would give the WC an actionable grievance against the White Court (assuming it could be proven to a given standard blah blah).  That kind of grievance can be settled sometimes with a weregild or higher stakes including war depending on the moods of the Accorded nations.  My understanding with the WC-RC war was that both parties wronged each other, so other nations had an out to stay neutral.

I'd imagine they'd have to be animals he has a connection to, psychologically.  I can see a wolf, based on his associations. Or a hound dog, because of his profession and mindset.

I don't think he has a lot of associations with lizards or horses, puns aside.

Harry is going to live in a magic castle in the middle of Chicago and call himself The Wizard Of Chicago. That seems fairly flagrant. A lot like a middle finger to Scotland. And Wizards should move with caution before starting a loud fight in Chicago lest they start to find themselves targets of Hellfire missiles.  And if he gets married to Lara, the WC could find themselves in a war with two groups of monsters. Lara's accountants and the Fomor.

   I think there isn't a whole lot Harry can say to Carlos at this point as long as he is Winter Knight.
I think what happened when he and Molly attempted to make love did more than cripple him physically, it left severe emotional scars as well.  I realize he is a Warden and his duty is to enforce what the Senior Council rules, but he seemed to have drunk the whole glass of kool aid as well.  Does he really think Harry is a monster?  Does he really think it is Harry's fault that his fellow Wardens were killed or worse by the Black Court?

Do you honestly think confessing to Carlos that Thomas was his brother would help?  Or would Carlos have the same attitude as Eb?  Or more to the point if this did get around that his half brother was a vampire, the Council would be even more against him.Except Eb doesn't share them, so in the end he might make it worse not just for Carlos but Eb as well.That wouldn't get him very far, especially if Carlos already didn't trust him.Except Carlos seems perfectly willing to become Morgan, that is the problem.. Harry is back to being under the Doom.

I think the actual events are different than Hankthemoose described.   Based on what was described Dead Beat, Lea challenged Mab in some way.   Mab stated that Lea thought the atheme gave her that right and she showed her the error of her ways.   

We know from later books that this is when Mab realized lea was infected.  We also learn that the challenge was related to Harry - specifically Lea was desperate to help Harry against the necromancers in Dead Beat.  That desperation was presumably what tipped Mab off about the infection as it is not typical of Fey.  But I cannot remember which books gave this info, but they were late stage books (cold days perhaps). 

I also believe that Mab was holding the Atheme during her meeting with Harry during Dead Beat, but I am a bit hazy on this.  If correct, then Mab had already taken the Atheme from Lea and cleansed it.   Certainly Lea was aware that the athemea was how she was infected and holds a grudge -- which she explained to harry to justify Mab using her to help him during Changes.   Mab was doing a favor for Lea to allow her to get her revenge on the red court - otherwise lea's services would have been much more expensive to Mab.