Would it be a good idea to have the engine hooked up to some kind of monitor to watch the spark events to see exactly what’s going on?
There has to be way to determine whatever is going on here.

I've used a timing light on plugs that are suspect. Just shine the light on a clean paper/cardboard piece while increasing rpm's. Up to a certain rpm, your eyes will notice a misfire or erratic firing. Start or with #1 for reference then proceed to #8. If it's erratic with a new plug, then problem is upstream of the plug. Just some off-the-cuff thoughts here.