Well you may be off track. What are the two voltages reading with key in run compared........blue "run" and the red coming INTO the switch? That will tell you if the drop is in the switch/ or connector, or whether the drop is upstream in the red? I'm missing that somehow. If those splices are "solid" whether they look bad or not may not be the trouble.
How does the "big red" (battery feed) get through the bulkhead? Is it still "the connector" or drilled through and wire straight through?
