What's interesting is that neither the keyboard nor the mouse work individually. Either both simultaneously became faulty or something is wrong inside the Mac.

These fuses are soldered onto the logic board. You will need a continuity tester/ohm meter/multimeter to test them. The freezing and unfreezing worries me a little, it seems that the Mac is trying to communicate to your ADB device(s) and is sitting waiting for a response. I'd definitely check the fuses, but beyond that it might be something fried on the logic board, possibly from static discharge somewhere along the line. It could even be a capacitor or battery that leaked onto something critical for ADB. It wouldn't be a bad idea to give the logic board a good washing.