[GRutter]

So glad you got it figured out and happy I could help.

Yes, it is absolutely safe to run your car with a jumper between the two studs on the junction box. It effectively only removes the ammeter from the circuit.
Use the same guage wire as currently running to the ammeter.

Alternatively, you could put both wires on the same terminal on the back of the ammeter until you get a replacement, but of course that would require that you unscrew the dash.

The only issue is you won't be able to see your charging or discharge rate. I suggest you use your battery disconnect switch, if you have one, until you replace your ammeter