Sounds like you put too big of a load on the circuit and you fried something inside the pac harness. I think audio circuit has a 10amp fuse. It doesn't mean that the PAC can handle 10 amps though. Voltage drop isn't good. It means you exceeded the fuse or the PAC harness. Since the radio still works but it acts weird seems like something shorted out inside the PAC.

Lesson learned I hope