1-yes was how it was measured. Thought 14v may have been excessive for that vintage. Now that voltage is normal in modern vehicles.

2 yes measured on vs terminals. That was a value that I remember that was suggested, I have known to be mistaken.. Once or twice...

I have had the gauge clusters apart prior to the mortality. The fuel gauge had a broken wire before the bimetal coil. I had put the broken wires together and had continuity without resistance, or very little over both gauges. After re assembly of the cluster I then checked the continuity to the plug connections and the ground connections.
As to Eric's post of 5v, now that you mention that, I do remember reading in the volvo manual I do have. It states 5.5v for the stabilizer, somewhere in the 8 or so sentence paragraph about it.

What I've learned.
5v not 10 (wouldn't that torch the gauges? 10v)
14v power feed to stabilizer is ok
High resistance in the gauge itself is bad (don't the sensors create resistance via ground?)
Check chassis grounds

I'm a body guy by trade and have worked @ several dealerships. I can fix anything...but anything beyond basic electrical, I lack the knowledge to fully understand.

As for Nebraska, come to Kearney the weekend of the 18th for Cruise Night. It is a good time, especially sat night when 8mi of 4 lane streets are clogged with classic cars crusin... Including one volvo..