In my experience it doesn’t necessarily have to be 3 events - it could be one major event also- for example if he books a tour with an artist or something like that.
Assisting is tricky. I think it’s because your lawyer is trying to prove that he is the best in the business. If he’s assisting on a convention that travels around the country (like Pulse for example) and that choreographer has a great resume (say like Brian Friedman or something) then I would imagine your lawyer could argue that your son is a pretty big deal. Your lawyer knows best. I imagine your son will need a couple of other jobs to show that he is making a living as a dancer and that he is at the top of the business. I think that’s probably why he said assisting at a studio is a no…
I know that’s not great news but keep going! The fact that he’s created opportunities for assisting in 2 weeks already shows that he has talent and he has been seen by choreographers. I encourage him to try and assist on actual jobs- music videos, shows, television etc. That would probably be better than studio level assisting. The jobs will come around and if he has DDO on his side already then the last piece of the puzzle is the job offer or offers.