I am by no means an expert in log analysis and have absorbed most of what I know by reading posts by the development team and those more experienced than me. For example, Randy gives an excellent rundown of his log review in this topic.
If you use Mission Planner for log review, you can hover the mouse over most entries and see a brief description of the value in the lower right corner of the window.
Tridge gives an excellent talk in this video, though he focuses on the Plane platform and uses the more command-line intense MAVExplorer tool for analysis.
There’s also an online tool for log analysis that can be helpful in presenting data in an alternate way.
However, I have not found a single source document that will answer all of your questions, unfortunately.