It might be more helpful to revisit the core curriculum, particularly the lessons you are having the most difficult time with, and go from there. I see where you are going with trying to figure out specific calculations but you will be more efficient with your time by revisiting LSAT core content than focusing on the minutiae of LSAT algorithms.

You have an interesting perspective; I do not share your opinion concerning the LSAT being a sort of gamble, however. You noted yourself a sense of mastery that has come with working on substitution questions. If you can put organized effort into something to obtain a particular result that hardly sounds like a gamble. The percentiles indicate that overwhelmingly often than note, you will not score in the 90-99th percentile. That is OK. If a holistic concern pertains to obtaining the highest possible score on the LSAT, you should consider working/strengthening your other parts of the application process as well. LSAT is one, albeit arguably one of the most important, measures to which gauge your strength compared to others. Just food for thought.