1) It was either 18 or 20 gauge, but you could use thinner if you wanted. It's not carrying any measurable current or anything.
2) Yes, I had initially done everything through the connector, based on a guide I found elsewhere on the net. That setup had issues and didn't work properly, which is why I removed it from my post earlier in this thread. The mic did not work at all and the audio was way too quiet. I guess the audio on the connector is a much lower level than the audio on the speaker wire. Don't forget, the final setup is exactly the way Rugged does it. There's obviously a reason they go through that trouble versus just a plug and play connector
3) Here's my thoughts...the PTT is on the board connector. If you are going to the trouble to do the board connector, you might as well pick up the ground there (pin 1). That ground will work as a ground connector and also as the negative speaker connector. At that point, you only have the speaker positive and mic left to do. The mic is the hard one, not gonna lie. The speaker + is pretty easy since it is a short wire you are cutting and soldering, not a board connection. All that said, if you are worried about soldering, you could just buy the harness that plugs into the speaker outlet AND the mic port on the front of the radio. Then it would be totally plug and play. It just won't look quite as clean since you have the visible wire plugged into the mic port on front. It would be a lot easier though and would be sure to work. Here's the cable I'm referring to: https://www.ruggedradios.com/index.php?main_page=product_info&cPath=53_48&products_id=2437 With that there's no opening up the radio or anything.