76 dart sport fuseible links

Tool.Man said
3. I put the ammeter in series with a bulb and a 12VDC source just long enough to move the needle on the ammeter.

Don't think a shunted ammeter can be tested that way. They work more like a voltmeter.
Some other guys here have some experience with them. @67Dart273

Tool.Man said
4. Continuity, measuring from either side of repair.

Good enough for finding major faults in the connectivity

Tool.Man said
5. I measured zero voltage at the ammeter to ground.

Then its not connected to the power source.
When the circuit is open downstream, everything above the switch or open should be at the same voltage. In this example, 12.8Volts.

When the circuit is complete, everything before the load should be at the same voltage

the current through the meter itself is milliamps

Tool.Man said
That takes me back to identifying the shunt. A11 and R16 disappear into the harness. It would seem I have to unravel the harness to uncover the opposite ends of A11 and R16.

Nope. We can use the shop manual.

Tool.Man said
I suppose if I do find the opposite ends that there will be a wire between them and that will have to be the shunt. Then, having identified it, I can take the telling measurements. What do you think?

Yes there is a heavy wire between them.
Lets work from a photo and my copy of the shop manual. if you post some photos of your car's harness etc then that will be better of course.