Re: Jack being buried, I don't think the writers care all that much about the specifics of Jack's immortality, as evidenced by him crying in the car with whatsisname as he kills himself in "Out Of Time."

I think he died over and over again, but since it was a penance that he undertook willingly, he didn't go insane, he thought he deserved it and took it stoically. And he was probably only semiconscious.