Also it’s a 1995
I'm sorry but you are wrong. The woodruff key secures the starter driven gear to the engine crankshaft. If this key was sheared the engine would not turn over. Yes, it would affect the spark of the plug because the flywheel would be spinning while the starter is engaged, but the engine wouldn't even be turning over to fire. I do have some firing just when the starter is engaged and disengaged.A sheared woodruff key would not affect the exhaust or the starter, it would affect the ignition making it fire the plug at the wrong time.
It sounds like your issue is a bad CDI. Is your CDI an (or any other ignition parts) aftermarket one or OEM?