Hello Autolite and Welcome to MLMF!
All I can say is Wow!
You're obviously very familiar with your machine and the way you've presented your suspicions of what may be failing are so detailed...I'm not sure what to suggest from this point on. Depending on how fond you are of the mower and trying replacements parts one by one is probably more expensive then the residual value of the machine's net worth.
The only option I can think of is a visit to your local repair facility that specializes in models like yours as they may either recommend the most common (suspect) parts that fail or (perhaps) a salvaged unit in their inventory.
I hope someone here has experienced the same problems with the identical model (or something very close) and can add something more useful that what I've offered. I hope you stay in touch and let us know if you resolve the problems and your progress.
Thanks for posting,
Mark