You are correct, a bouncing tach and flickering test light on the coil usually indicates a functioning CPS. You did not say if you checked the spark on the center coil wire. If you have spark there, put the CPS on the back burner and look elsewhere.

Given a functioning ignition through the coil, but no spark at the plugs, my next best guess is timing, especially when the breakdown is sudden, and happens when the car is running.

You didn't say if you confirmed the belt was intact and turning the cam. Another way to confirm the cam is turning is to take the distributor cap off and watch the rotor. If the rotor is turning while the engine is cranking, the cam is turning and the belt is intact.

If all that is good, suspect a jumped timing belt.