That’s not a little rich. That’s very fat. These threads all run together after a while but aren’t these plugs out of an engine that is using manifold vacuum because the carb is fat?
If so, fix the carb BEFORE you start with timing. You are far enough off that it’s cause you to jack more timing in it than it needs.
Edit: I just went and looked and if you are sure you have 9.9:1 compression there is no way, no way it needs that much timing at idle with your cam.
Not even close.