Obi-Wan is a bit tougher, but I think he is clearly an NF. His whole dispute with Han over the nature of the Force and spirituality illustrates that contrast. "Hokey religions and ancient weapons are no match for a good blaster at your side" is the most ISTP thing ever said. He emphasizes practicality, concreteness and things that logically work and make sense as opposed to Obi-Wan's metaphysical spirituality and sentimentality.
I also think Obi-Wan is a clear introvert, and it's only the last letter I'm not sure about. But ultimately, I just have a "feeling" that he is a J, if you will. The way he plans things out during Luke's training and when he sabotages the Death Star suggests this as well.