Well, I decided to do a quick swap to check whether the cluster housing and such was bad, but the replacement unit I put in displayed the same issues as my original, so I'm (for the moment at least) ruling out the cluster as the culprit.
Gotta get this thing running right, meaning I'm reduced to going through the motions you noted and have started tracing each circuit from it's particular cluster plug backwards. Tedious, but I can't see any other realistic options to finding these problems.
Next time I decide to rescue a car in this condition, somebody please get proactive and put me out of my misery to come.
