how to adjust vacuum advance
With the vacuum connected you should have about 50* at about 3000rpm.
Without vacuum, you should have about 34* total at around 3000rpm by turning your dist in small increments.. Once you get 34*, bring it back to idle and see what you get. You should be between 12* to 18*.
If you can't achieve these kind of numbers, your dist will need to be recurved.
Once you get 34* total you can adjust the vaccum from there with the allen wrench in the vac pod.
you don't want any ping whatsoever.
Your plug gap seems excessive. I would not exceed 38 thou gap.
Jim