THAT is a low power supply to the cabin (or everywhere)
Does it have the OEM amp meter in it still, and do you know if the MAD electrical bypass has been done?
Might also want to have a good look at the bulkhead connector for overheated wires and connectors.
These cars never had a good supply for electric accessories and the radio cutting out is a classic sign of low voltage.
You have a lot of reading to do along the electrical upgrade lines.
