2) Connected the Isolated Ground (from my ground post) to the ground pin of the IGR receptacle.Dangerous and against Code. In the event of a hot to chassis ground fault event, of a piece of audio equipment plugged into the IG receptacle, there is not a low resistive path for the ground fault current to travel back to the source, the electrical panel. The breaker that feeds the branch circuit will never trip open. In fact there is a good chance the chassis of the piece of equipment would be Hot, energized, with respect to any other grounded item that is connected to the main electrical service equipment ground. An electrical shock, or worse, electrocution hazard.
I also suggest you reread erik-squires and gs5556 posts.
Again.... The earth does not posses some mystical magical power that sucks nasties from audio equipment. If anything it can add noise. You won’t find any well respected EE that will tell you otherwise.
3)#6 is bare minimum. You can use larger.
I changed the 4awg solid copper bare wire to 6awg insulated strained wire to match with the NEC code.
Did you click on the Link with the video I supplied in an earlier post?
https://www.youtube.com/watch?v=WlnFNTay-9Q
That guy talking helps write NEC Code.