I would start with checking the timing.
I really would check the balancer marks at true TDC that is verified by piston movement. You said at one time your timing was set to 4 degrees and now it was back to 2 degrees.Another thought is Harmonic balancers can slip over the years. There is a hub that mounts to the crankshaft, then a rubber insulator, and then the outer wheel that has the timing mark. Inertia over time and rubber rot can make your timing marks fall backwards. It can be verified by checking true TDC of your engine. A dial indicator is best, but sticking a screwdriver in the spark plug hole and really paying close attention to when the piston goes up and then down and has the degree or two where it is at the top. Find that and see if your balancer mark points to zero.