Try adjusting the idle mixture the way I learned to about 60 years ago- - - -turn the mixture adjusting screw clockwise (lean) until you see a drop in manifold vacuum, then back it out until the vacuum maxes out. Some people claim that the acceleration just off idle improves if the mixture screw is set about 1/8 turn richer after the max vacuum is achieved. Unless you have a leaky intake valve, that should stabilize the vacuum and eliminate the slight pulsation of the gauge in your video. I've seen Pertronix triggers that can be moved on the distributor cam a little, which results in inconsistent ignition timing between cylinders. A drop of RTV gasket sealer between the cam and the trigger wheel might help avoid the error.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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