This is probably going to be taken the wrong way, but I read the whole thing and it sounds like just a bunch of whining to me.
The whole "I'm a professional sax player, I'm too important to do any promotion or actual work other than playing my sax" routine just doesn't fly with me. He picked an instrument that's mostly only good for one genre, and it's a dying genre that's part of a live music scene that's also dying.
The guy thinks he should be automatically making a living just because he can play an instrument? That's not how society works. Unlike banking or plubming, playing music is FUN, that's why we do it, and that's why people are willing to do it for less than he is. At the same time, I don't expect a club to book any of my bands just because I exist. It's a business arrangement, and we make them way more money than him and his little Jazz trio. Part of that is constant promotion, and part of it is putting on a show that gets people into clubs.
The reason I personally don't play jazz is that it's generally pretty boring. The music itself is great, but people treat it like pleasant background music for their wine bar or Sunday Brunch. I'm not interested in providing a pleasant background for conversation, I like to engage the audience and make it a fun party.
My advice for Dave Goldberg is to either play better or get a real job. If you put on a show that's compelling and fun and entertaining, getting 50 people to come to a club is no problem. If you can't do that, why should anybody pay you for providing little to no value to society?