Sounds like the timing is retarding causing the lower idle speed and dying scope wrench up
I have had the same deal, problems, on a motor with a big cam and a not real loose converter whiney
Changing the advance springs and shorting up the mechanical advance slot fix it by being able to set the idle timing in gear at 14 to 18 BTDC and have right at 34 BTDC full advance over 1800 RPM shruggy scope twocents

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)