Gonna' reply to 2 and 3.
2. Generally, a single rider line will skip most of the queue, so I wouldn't use it for the likes of Ministry or Monsters for your first time around, nor Bowsers Challenge if you haven't seen the queue and want to. Every other attraction listed you can skip the queue as there's not much (unless you want to see the Squawks and Cranky AA in Mine-Cart.).
3. It honestly depends on ops and the attractions themselves, once Ministry is up and running to a good capacity, that single rider is probably gonna' be one of the best in the whole park. But if it's at more of a limited capacity, you could still be waiting a bit. Monster's single rider could be very good as well. All the other attractions are two-across seating, which is honestly not the most ideal for quick single rider lines. It could be decent like Velocicoaster, or absolutely not worth it like Hagrid. Thing is, it's a big wait and see on how they'll go with general crowds.