The exhaust camshaft knockpin was bent by the timing sprocket, due to force exerted counterclockwise, by attempting to loosen the crank pulley bolt while the camshaft gears were blocked by a rag. (Never do this). The hidden damage retarded both valve timing and ignition timing. The distributor is driven directly by the exhaust (front) camshaft.
The force applied at the time (or later attempts to remove the bent knock pin) caused hairline cracks at the perimeter of the camshaft at the pin bore. A good used camshaft was installed and the engine seems to be working properly.
Thanks to the group for advice, especially the kind comments of Ray O.
Jack