As far as the intermittent ignition problems, it wouldn't be ground related. Have you bothered to change the condenser? It may be breaking down internally after it gets hot. I did see a vehicle like this too that the neutral safety switch caused a similar issue. I have noted that I have seen the feed to the coil as low as 5.3V with the key in the run position.
P.S. How did you relocate the coil to the right apron? I'd put things back here they belong, check voltage. If that is good, change the condenser. See what happens.