We seem to be caught up in assuming an ignition problem. Could be something else too. It goes rough under any kind of load, right? But runs OK with no load? So as cylinder pressures go up the fire goes out irrespective or RPM?
Did you check for water in the gas? How much alcohol is in the last tank of gas you bought. Alcohol attracts water and mixes with it. The engine can tolerate small amounts of alcohol/water mix but it can cause problems at higher concentrations.
Since it does its thing when cold also, I'll rule out detonation but I've had that problem twice in the last couple of years both times I suspect a lean condition from excess alcohol.
Another possibility is cross-firing either inside the distributor cap from moisture or induction between spark plug wires -- possible but unlikely; make sure the plug wires don't run parallel but rather cross as close to 90 deg as possible. Since it did this before you bought all the tune-up parts we can rule out infant mortality on those parts. But just for drill watch the engine run in the dark to check for arcing wires and also check the spring tension on the points. If it's low they can bounce causing some of what you're describing and I'm hearing on the video. I've seen new rotors short out to the distributor shaft so look for carbon tracking there. A bad condenser can cause similar problems and I've seen new ones fail more often than old ones. Coils usually act up when hot but can fail cold too.
Plugs are dirty? perhaps from the misfiring perhaps from carburetion. Clean them.
How about valve timing? If you have a fiber timing gear, as car engines did, it could have given up the ghost and slipped a tooth. If it goes completely or even any more than a couple of teeth the crank will wipe out a cam lobe and you'll have to pull the grill to change cams. Generally, if cam timing has slipped, the engine will run at higher RPM but won't pull a load below a couple thousand RPM. Usually the gears fail catastrophically but not always. You can change the gear without pulling the cam if you replace the gear with an aluminum one and heat it before you install it.
Did you shake the rotor to check for a worn distributor bushing, which will let the timing bounce all over the place? Maybe a broken spring in the mechanical advance under the point plate. How 'bout a bent distributor shaft?
Now I'm out of ideas
Best of luck. Proceed logically from what you know toward what you don't. Assume nothing. Leave no stone unturned.
