No power.. Ammeter questions.

Do you have a an ohm meter or multi-meter with resistance measurement?
If so, with power disconnected. Test for continuity through the ammeter. That is, one probe on each post. This will verify that the ammeter shunt is damaged - which seems to be the situation. But, if not, then its likely there is a loose or damaged connection - and when you bypassed the ammeter it was the moving of the wires that made the connection.
The black ring terminal is the only thing that I see that shows damage in the photos. I'm talking about the copper corrossion and damaged insulation.

no radio, turn signals and wipers doesn’t work.
All of these require the switch to be in Run or Accessory. Additionally they all are fused.
Check the fuses and if they are good use the meter to check for power to the fuse box.

Take a look at the basic circuit layout here, and see if that will help you diagnose the situation.
Understanding Charging Systems with Ammeter