1.) What if a Killer's body is utterly destroyed? If Digo finds himself on the wrong side of a flamethrower, or someone decapitates him after death, or mails his arms and legs to the four corners of the world... in what condition does he return?
Paths are not quite as different from one another as some might assume. In essence, a killer is still a spirit made flesh, same as a shadow is. As such, a killer whose body is utterly destroyed would find it more difficault to return to life (and the process might take longer, roleplay-wise), but failing the ability to re-possess their own bodies, a killer would return to life in the same way a necromancer does (being the path's neighbor).
"Their rebirth is similar in this way; they return as little more than husks, and gradually build back to their full human visage."
Good question though. Made me think for a while.
2.) What if a Killer's body is removed from Harper Rock? Does the Killer reawaken in, say, France... or do they create a new body? Can they even find their way back into the mortal coil?
I'll leave that up to writer's choice. I would imagine it would take longer to re-possess a body that is physically a long way away, but it would be possible once the spirit had returned to the real world, as it was possible for the wraith guides to move to harper rock. But you could roleplay the alternative method of returning to life if you prefer.
3.) Does a Killer's body decay while uninhabited by a spirit?
Yes, but more slowly than normal, which could give a human a certain amount of pause, but wouldn't immediately violate the vampiric secret.
1.) I was of the understanding that the Shadow Realm existed SPECIFICALLY in Harper Rock; hence, Fadewalking elsewhere (according to David) was impossible. So, are all Wraiths formerly of Harper Rock (with the exception of the Wraith Guides)?
No the shadow realm does exist world-wide, but the tare is only present in Harper Rock. It took the wraith guides great effort and time to move to harper rock, and now that they have, they are unable to return to life without aid, as they still died elsewhere, no matter where their spirits are being projected. So, almost all wraiths would be of vampires that died in that part of North America.
However, the summon wraith power (as a thrall) can draw a wraith from further away. Forgive me if I'm contradicting myself on that matter, but I can't recall having stated anything to the contrary in the past.
Remember, though, that wraiths get swallowed up by the shadow realm after enough time has passed, or they go insane. Any wraiths you summon are likely (80% of the time) to be unintelligible, or at the very least absolutely insane, and certainly not older than most of the wraith guides.
2A.) When you Summon a Wraith, do you enthrall a Wraith from the SR, or only one that has been able to manifest?
From the SR. But that in itself isn't bringing them back as the ritual does, exactly. A summoned wraith is bound to the vampire, so it couldn't return to life unless it was first dismissed.
2B.) When a Wraith is banished, mechanically it ends up in the Shadow Realm and doesn't come back until you Delete and Re-Summon it. Canonically, can the same Wraith be re-summoned?
Yes.
3.) What powers do "normal" Wraiths have? Can the average Wraith, for example, read the CrowNet if they were a Telepath in life?
Not the average wraith, no. They are more like tormented spirits, so they wouldn't have the intelligence to do anything complicated like that.
4.) Will we be able to, at some point, play a Wraith Character?
You already can. A ritual can bring a dead vampire back, turning them into a wraith.
5.) How long is it before a vampire subsumed by the Shadow Realm becomes a Wraith? Reputedly, Cobb MAY be a Wraith, which leads me to think that prolonged exposure to the Shadow Realm could have unexpected effects.
I might be forgetting something I've already said, but aren't all dead vampires wraiths?
6.) Will the "Raise Wraith" ritual work for our Wraith Thralls?
More of a mechanics question.