1. The altered AC requirements aren't a requirement that they show up less, it's something that can be done if it's good for the plot. It's meant to enable stuff like "Bowser kidnaps Peach in February, and it takes until June for the protags to reach Bowser" without Bowser idling out in the middle. That said... Plot-PCs are meant to be more like recurring characters than main characters. If you want him to move on to the Morning Star or Pericles full time with castmates, you'd probably have to switch factions.

2. Any of those sound fine, so long as he only has the capabilities of a normal human when he arrives.

3. He won't get a response. Whether that manifests as a "call cannot be completed" or just no one picking up the phone is up to any player that tries.