Yes, his mom did give him a blood connection to the US. Even if you want to argue that Obama has a closer connection to his mom than his dad, it still doesn't make him a NBC.
Marie had no relatives here, while Obama had mother and grandparents, and his grandparents raised him.
The Constitution doesn't say that being raised by your grandparents makes you an NBC. So this discussion of loyalties is kind of an irrelevant side argument to what the law actually says. NBC is not proof of loyalty to the US, just an insurance policy to protect the US from a serious possibility of foreign influence. Marie's situation is still NBC, but provides a loophole around the intent of NBC clause. She still is NBC.
For their definition of NBC, they don’t refer to Vattel but common law. Some are unconvinced by that reasoning. I find it completely reasonable, and think other courts will take the approach the Indiana Court did.
Yeah, that is probably the closest that the Supreme Court has ever broached the topic of Natural Born citizen status and is currently the established precedent. However, it is difficult to discuss the relevance of Wong Kim Ark when we don't know where Obama was born yet. Once his place of birth can be established, the Wong Kim Ark argument would be a little more persuasive, if you accept the premise that it was decided correctly of course. However, if Obama ever lost his US Citizenship or voluntarily took up another citizenship voluntarily, then there's going to be a problem.
So, the divided loyalty argument is not so much pertaining to thoughts in the mind of a President, as it is a matter of law between nations. The Founders sought to avoid such entanglements and intrigues, and legally structured eligibility to office in the executive branch in such a way as to preclude them legally, which was the only means at their disposal.