I disagree with much of your post, but the first point bothers me the most. If the trilogy were about Luke's disillusionment and fall, I would have been much more interested. You are filling in a ton of back story that I can see making sense, but you can't just handwave it in, especially with a character as important a Luke Skywalker. I can see a creative and emotionally compelling series about how he deals with impostor syndrome and I could even see it ending very badly for him. Treating that character arc as a sidebar misses the point of the entire saga.