Great job. I did not understand why you needed a ball jointed spark plug tool though? Or a magnet one (normal ones have either magnet or foam grip but they allmost all of them grip the plugs their own way). Nice tool though, i might get one some time :) A tip on torquing, don't do it in steps, just torque continuously until it clicks. Reason being each time you stop, the screw/plug sieze a little and you risk clicking imediatelly when starting again and thus getting too low torque. Copper paste or aluminium paste is what i normally use for plugs as it leads electricty well for the negative and prevent seizing plugs. Never tried your version though.
