1) Good heavens, yes. Discursive meditation evolved out of the Greek philosophical practice of writing little essays on the subjects you wanted to think about -- the Stoics were especially fond of that, as it gave them practice in focus and concentration. Many writers also find that the process of writing is meditative in nature, and allows them to unpack concepts and themes in a way that other methods don't. I don't happen to know of a book about this specifically, though there may be books on journaling out there that cover it.

2) Yes, if you work with mental-plane phenomena -- meanings, values, insights.

3) I've never seen any discussion of it outside of my commentariat. Several people have brought up the idea, and I'm hoping that someday an experienced RPG player who's also an occultist will write something on the topic.