1. Usually a star washer means ground. Though, in that area, there usually isn't a separate ground wire for anything. In '68 there was a ground wire added to the instrument cluster that goes to the pedal support brace. You might have to just try to get in there and look around for a wire hanging or an empty hole. Not easy, I know...
2. Yes, the radio power wire is Yellow. And that looks like the correct type of connector for it, too.
3. Do your headlight doors work? That is the connector for them. Correct colors, too. I believe it is in the correct location, as well.