Regarding the events on the Perilous, wasn't Rook supposed to be part of that crew?

Yes, the story Grimm told here didn't quite fit with what we'd already heard in book one, but that could be either Grimm lying to Abby or Jim changing things.

I was disappointed in the treatment of Rowl, he seemed too insecure and petty. Book one he had utter confidence and a complete belief in his superiority, this one he seemed far too concerned about not being upstaged.

I'm also disappointed in the fate of Predator.

1. We have been told that Nicodemus has a very specific target in mind, ostensibly kept in the Labyrinth of Daedalus.  What is Nic trying to get his hands on and why?
I suspect a powerful "fallen" related object.

2. Nicodemus apparently called in a marker from Mab to get Harry on the team.  Does he have a specific plan for using Harry or did Mab twist his request?  Which of Harry's capabilities will he admit to needing, and (given that this is Nicodemus after all), which abilities is he scheming for Harry to use?
Harry being previously dead will be important, plus Harry is good at hitting people.

3. Jim has mentioned that the book will be "Ocean's Eleven".  Who else did Nicodemus recruit?  How will they interact with Harry?
I suspect most will be new superbaddies that Harry's never seen before. Some will instantly hate Harry and vise versa and some will later become allies.

4. Harry's general method of operation is to call on his friends for help.  In this book, Harry is (initially) allowed one extra backup member on the crew.  Who will it be?  Which of Harry's other allies will "interfere" before the plot is over?
Butters, but because "Polka will never die!" Harry will be forced to use someone else. His second choice will probably be Will or Thomas. The swords will make an appearance near the middle to end of the book though, and I suspect most of the JL of Chicago will show up near the end for a rescue. Ivy might make a guest appearance as well.

5. This is a Denarian book, so (unlike the last "end of the world" showdown), the Swords will almost certainly be present.  In fact, there have been various hints...  Which Sword wielders will appear in the next book and how will their interference/help affect the plot?
Sanya will be there, and I suspect one other sword will come into play.

6. Mab is apparently against Nicodemus succeeding in this heist.  In the Cold Days, we found that Mab had complex reasons for wanting Harry to kill Maeve.  What are Mab's reasons in this book?  Is it simple thwarting or is there something deeper?
It'll depend on whatever it is that Nic is after, but I suspect him getting it would be very bad for Mab and she's opposed to it.

7. At the end of Cold Days, Harry needs to stay on the island to keep his growing headaches at bay.  The start of Skin Games implies that those headaches will need to be resolved by the end of the book.  Who or what is causing those headaches, and how will the whole thing get resolved by the end of the book?
I don't have a good answer for this one. 
8.  One of the key components of the "Ocean's Eleven" movie is that there is a final twist/reveal.  Given that we've got Nicodemus, Harry, Mab, and potentially Hades (and who knows who else) all trying to get the better of each other, if there's one thing you can count on it's some sort of last minute quintuple-cross.  What will be the nature of the twist and how will it all fall out?
Nic will reveal that he's after something completly different that what everyone thought, but Harry will be "sorta" ready for him and he'll pull of weak victory.

9.  (Extra Credit) There are many WAG ("Wild A$$ Guess") theories on the boards, some crazier than others.  Write up to three WAG theories (or make up your own) you believe are correct that will be confirmed (or at least have evidence in favor of) in Skin Games.
The thing that Nic is REALLY after is the soul of Magaret LeFay.

10. (Extra Credit) This is that "free form" question where you can come up with anything else you think will be in this book.  Specific quotes Harry might say (will he actually quote Ocean's Eleven?  The movie will have come out already in Harry's timeline)? Tidbits about the White Council? The fate of Molly? Write down anything you want.  Note that whatever you write must be specifically mentioned or hinted at in Skin Games in order to be worth credit. 
Harry will meet with several people that have died possibly: Susan, Kim Delaney, Harley MacFinn, Malcolm Dresden, Magaret Lefay.

Cat-Sith:   Not knowing this character too well, it is difficult to understand what would motivate him to disavow his Queen.  However, he is the leader of an entire species.  It must be demeaning to take orders from another regent.  Especially, it must be demeaning to be ordered to take commands from Harry Dresden.  And, considering the first time we see him after the infection, he tries to kill Harry.  And, considering that he stated how much he wanted to make coasters from Harry's spine in the beginning.  I think Cat-Sith was promised the opportunity to kill Harry Dresden (an instinct) if he accepted Nemesis.  Even so, Cat-Sith resists to some extent.

I would say that it needs some consent to really work but that anyone can be taken, I think Cat Sith was taken, not given, which is why Cat Sith seems less effective than he should have been. Those that give consent become agents of Nemisis, those that are taken become puppets.

1. There were 4 wolf belts. Bonus points how many people wore the belts?

Should be 5 people wore them if I recall correctly, but I dont remember if we see all 5 actually transform.

What about the paintball gun with garlic and Holy Water rounds? Or was that never used...dang it I can't remember...

Harry used it against fake Mavra to kill it.