4) Littlefinger is not affiliated with any faction. His entire motivation has been trying to bag Cat and will be his undoing with regards to Sansa.
I think you're mostly right here with only one flaw.
Littlefinger is in littlefinger's faction I agree there. I also agree that Sansa will be his undoing.
However littlefinger's motivation wasn't to bag Cat. He knew there was no real chance of that. He was motivated by the desire to watch the system, that deemed him unworthy of Cat, burn. Sansa will be his downfall because the thing that motivated him to become the best player in the game reminds him so much of what he could have. Littlefinger was so good at the game because littlefinger had nothing of real importance to lose but he now has the beautiful daughter of his first love in his hands and is revisiting those feelings all over again. He lost Cat to Brandon in a duel. I don't think he'll be willing to give Sansa away for some lands and titles.
So littlefinger will have insulted the heir of the vale when he already has a hold on the region that is tentative at best. We've seen what happens when men make marriage pacts.
Sansa won't outsmart or outplay Littlefinger. I don't think anyone can beat littlefinger at the game of thrones. Sansa's power lies in the fact that she can make him quit playing the game altogether