Varying spark, out of ideas
I've had the thought of a bad ground but am unsure how exactly to check it. Could you go into more detail on how to check it? I am unsure of what should be grounding to what inside the distributor.
The ground of the distributor will not have any effect on cylinder compression .
Your compression numbers are very low,,,,across the board .
I believe that is where you need to give your attention .
If the cylinders are sealing,,(,rings and valves,),,,,then it should be camshaft timing related .
If it ran good before,,,,and now it doesn’t,,,,check your cam timing components .
Tommy