After additional countless hours of troubleshooting including:
- again checking everything a dozen times
- new wires,
- electronic module,
-direct 12v wiring and ground from battery,
- new cap and rotor
- and much more
I decided to remove the Pertronix distributor and switched to a used Mallory distributor that came out of a running Pantera (car is getting restored at the moment).
What can I say: Car started right up and runs like nothing has happened. I think you can imagine my face at that moment
I disassembled the Pertronix Distributor and couldn't find anything wrong, I even gave it to an retired electrician that worked in BMW development and is one of the smartest guys I know and he also couldn't find anything.
Fun fact on the side: The Tach that always read slightly wrong with the pertronix is on point now.