I think I can answer a few of these questions.
1. There is always room, but you must sign up at the beginning of a 3 frame series like right now. You seem to have figured this out already.
2. Yes, 2 would be the minumum required for a 4-6 commitment, or Daddog and Ghost Dancer would come visit you in dark suits and sunglasses.
3. CO can be anyone in the squad. The Special Events Arena squads are mostly mirror squads of MA squads, but they are in reality completely separate from the MA. Our squad (USMC) has changed and split in the MA, but we still operate under USMC banner in the Special Events Arena (SEA), and I am just a peon pilot in the MA squad, but CO for SEA.
Hope that helps. If you want to take time to get organized, hook up with one of the existing squads and fly as a guest to see how they do things. I am sure any squad would be happy to have some guests.