All the symptems point to distributor/advance problems. These years had the mechanical advance up top under the rotor. The inner and outer shafts would seize stopping the mechanical advance from working. It needs to be pulled, the shafts removed, freed up, lubed and reassembled. Also check the vacuum advance unit with a vacuum test pump. Vacuum advance unit is an economy device and comes into play at light,cruising throttle conditions.
I repaired many of these in my shop days years ago. You need to find guys that know these older systems meaning probably "OLD" guys.
