Check your voltage at coil positive post to ensure that your ignition coil is getting proper voltage. Should be in the neighborhood of 8 to 9 volts after running thru ballast resistor while engine running. If not at this voltage, check wiring all the way back to ignition switch,,,,,,or jump from positive battery post to coil positive for a short time drive to determine if your issues are resolved.

Wonder where your carb butterflies are at when at idle. The fact that screwing mixture screws all the way in makes no difference suggests a vacuum leak or you are idling in the transition zone. Although high idle vacuum reading does tend to contradict that.

Hopefully vibration dampener in good order and timing mark has not shifted on it. Backfiring and poor performance are suggestions of retarded timing,,,or severely lean mixture. How do your spark plugs look?

Assuming spark plug wiring is correct and no bad or burned thru wires. Run engine in the dark with hood up.