Not certain if appropriate for this issue this late in the game, but have found this tool very helpful in shortening analysis time on some of my own tough electrical issues.
Main downside is that is designed to use with blade type fuses, but with a bit of creativity can work with older cars using glass type fuses
Best to check out reviews for further info.
Once had a very random blowing of brake light fuse on our 71 Vette,,,,had spent days sorting it out. Used this tool and found the problem in short order.
