Re#2/#4) yeah, loosing the PC will simply things. Then perform a "Decent Tune-up". That will get your valves set to a relaxed 0.006"/0.008" and provide a solid base-line state of tune.
Re:#5) Bouncing tach could be a Relay issue (common).
Consider installing a full set of OMRON High Current relays.
Also, make sure the battery is at (or near) a full state of charge (12.84vDC) and the terminals are clean, tight, and sealed.