Of all the books of the Bible, James is probably the one that has most helped me grow as a Christian. It was, in fact, the first chapter of James that brought me back to Christian faith after a three year period of doubt that began my last year of high school. I realized my doubts were keeping me from moving on in my spiritual life.
James 1 was the text of the first sermon I heard on the first Sunday in a new church. I knew it was God speaking to me. He said, “Just trust me. Return to me and as you follow I will resolve your doubts. Stop tossing around in the waves and I will rescue you.” I recommitted my life to Christ that night. I have learned to handle my doubts and to whom to give them.
James was the first book of the Bible I memorized. I had just been to a seminar that stressed memorizing whole books. That was about forty years ago, and I could not recite those books back to you now. But my subconscious knows them and can bring them back when I need them. I, too, would encourage people to memorize whole books or whole chapters of the Bible, depending on length.
I believe you have concisely summarized the most important messages in James. As you say, the Holy Spirit will continue to teach individual Christians what he wants them to know in addition to these.