Unfortunately I found out the hard way. It finially got so bad it messed up the cap and rotor button, then it would not run at all. So I had it towed and the local shop changed the distributor. They are the ones that told me about the problem. They told me they used plastic bushings and that it was a common problem.
I do not know if you can check to see how much side play you have in the shaft. The only code I ever got from mine was a #3 cylinder miss. The problem did get worse over time and it took well over 2 years to finially die.
Like you, I spent a lot of time and money trying to find the issue. I finially gave in that I would have to take it to a shop. I just never set up a time to take it. I guess it set up a time.