Sounds like a plan! Until then. FWIW, I see in your distributor photo that the rotor is indeed lined up with the stamped 6 and that it has the factory hold down - so as long as the balancer mark was lined up right on TDC#1 - this distributor was installed correctly. Rotor terminals look pretty sad so it seems spark may have been jumping around due to cmp retard being off. Common cause of this is a worn distributor gear or bushings. We can check that out next. In the meantime I would go ahead and replace the cap/rotor - they seem to need it. Please still do the other tests indicated first.