As I wrote you by eMail, the Kerberos device is not recognized as a MIDI interface in the MIDI-in or MIDI-out combobox of the Kerberos App, because MIDI doesn't have a standard protocol for Windows to detect attached devices, only the MIDI USB cable itself is detected. I understand that you are frustrated that it doesn't work, but this is no reason to call it a piece of junk, it works for most people and they are happy with it.
It is unlikely that you killed it by unplugging the cable while connected, I designed it with some protection for the input side that it should even survive ESD events (like a sparkle when you walked on a carpet, but it might fry your C64, so don't try it), and the output is designed in a way that you can short it to GND indefinitely without damaging it.
But as I wrote you, too, if it doesn't work for anyone as expected, you can send it back to me and I'll refund it fully.