Spark Scatter
As you know I don't like to throw parts at a problem, but this may be one of those times
As long as you are convinced it's not a cam / drive problem, nor a distributor gear problem, my guess in no particular order.............
Pickup/ pickup coil, either loose or coil going bad, look carefully for debri (metallic particles) or rust around the pickup / reluctor
CAREFULLY examine the dist. for shaft play, both in the shaft and mechanical.
THERE WAS (I think orange?) a Mopar ECU that did a similar deal some time ago on this board............or at least that's what the member claimed cured it.........replacing the ECU