Steve, so if I am understanding you, the negative terminal on the coil has juice, but none of it is coming through the black wire that enters the distributor? If that is the case, either the wire is bad or the end is corroded. Also check to make sure your distributor has a good ground through the clamp down. Remove the clamp and clean up under it with some sandpaper, especially where it contacts the base of the distributor.

Sounds like you are getting close to a solution.

Don