Jim has directly addressed this if I remember correctly. Harry asked for and got the ability to save Maggie. He gets strength as the Winter Knight, Lea's temporary help to get Maggie out, and the continuing ability to walk. If Harry asked for a salary, I could Mab saying something "To people paralyzed like you actually are, the ability to walk would be priceless. This is your salary."

I agree. I think that the best evidence would be a continuity error in Peace Talks and Battle Ground. They were originally written as one book before coming out as a two-parter.

My suspicion is that the Chitchen Itza event was actually required to start bringing over the Outsiders to help the Formor. A fairly consistent part of the magic system is that the mood or atmosphere of the world matters. Dead Beat had Cowl messing with Chicago to "prime the pump" and Battle Ground showed that the fear of Chicago affected the spells cast during the battle. Since the big spell at the end of Changes affected so many people who weren't the Red Court, I suspect that certain spells would have been easier in the wake of the bloodline curse. I bet that it would have helped summoning an Outsider that is described as a peer to Mab. After being summoned, the Walker then helps the Formor assemble their forces and/or knock down some one like the king of the Tuatha as payment. It then starts assembling it's forces to assault Demonreach.

As for what the Outsiders get out it, beyond a Walker that gets summoned, is more chaos. Mab, Odin, and Uriel are chief forces in alliance for the current order among the natural world. Mab and Odin also established the Accords. Eliminating the Accords could pull away some of Winter's forces from the Wall and a massive global war would kill a lot of the people who could stand up to the Outsiders after they breached the Wall.

I hope the fact that Lara and Harry share a brother, but aren't technically related, is a source of joking or tension in 12 Months. Lara grew up when the Hapsburg chin was still a good thing and she's had way more incestuous sex than with her half-brother's half-brother (thanks Papa Raith). She almost certainly won't be bothered by this relationship to Harry but he probably will.

My personal favorite explanation is that the Council allows for flexibility in matters of self defense or defense of one's interests. We know that they allow for killing via magic in defense and I wouldn't be shocked in relatively minor breaks to some of the other 6 would be allowed too. One example is Dresden's wards that "suggested" people skip his bolt hole. Those were a gray area but, since they didn't cause permanent harm or major effects to the timestream and were in self defense, so they were fine. The mind fog grenades that Butters had only worked temporarily (if I remember correctly) and he got them while trying to help the humans of Chicago. My suspicion is that most Wardens would have let Butters off with a warning but tried to kill/capture Bob.

In defense of the OP, I suspect that honest-to-goodness deep love would inspire courage, hope, faith, and anything else that Malvora and Skavis would hate. It may not instantly cause them to be burned like a Raith but, since we know the White Court like weak prey, I bet it would cause them to not target people in a solid relationship. Maybe it's just my sappy side talking but I like to believe that real love inspires courage and hope. 

I listened to an interview with Jim that was mostly just writer-talk and his history (linked below). It did have some lore questions and someone asked about why Justine didn't mess with the island in Cold Days. His answer was "She wasn't possessed by Nemesis them". It was fascinating and out of left field. In Battle Ground, when Harry asked how long she had been Nemfected, she said "Mortal time is such a limited concept. A few years. Ever since she became close to Lara". That heavily implied to me that she was Nemfected all the way back in White Night because that's when she became Lara's assistant. With this WOJ, her statement almost certainly means an emotional closeness. Maybe Lara found out about Thomas and Justine resuming their physical relationship and it led to Justine and Lara becoming sisterly? I don't know but that's my best guess. We better get answers in the next book though.

Interview: https://www.youtube.com/live/NaAjmJWxnBo?si=t4GTFBqNV_KzInp4