Would mastering karma, by definition mean you no longer die, IE magnum opus? We all die due to something failing in us physically one day, and this would show up in the soul before it happened. And as you say when you get good and master this stuff, you should be able to see and correct problems like this. If you die doesn't that mean you didn't 100% master your Karma?
Also how does fixing the karma work? I get the part about making good choices, eat healthy, overcome with willpower, etc, but this seems like 1st grade level. I assume there is some intense hours of like, projecting and looking at your soul and probably some power building and even magickal workings?
Maybe you plan to explain this in another part of the series.