Anyway, its perfectly normal for a show to start with less than a full season. Sometimes a lot less. If the 1st season is successful, CBS will order a full season's worth of episodes for season 2. Its nothing to worry about.
Not likely. 10-13 episodes is the norm for streaming services. It will likely stay the same for every season.
But you're right, it's nothing to worry about. Different broadcast model reflecting changes in the past 30 years. The OP gave no reason why 13 episodes was problematic other than it's different from what Star Trek has done in the past. But if House of Cards, Daredevil, Man in the High Castle, and all other streaming shows can be successful with 13 episodes, then so can Star Trek.