Well I think they made the hood's interior black simply to make him look scarier, there's definately a body under there(or perhaps he's a skeleton and acts in a way Nostro does? If he is, you would be unable to see his neck and no hair would be visible.). His mask acts as his way to continue living, not as a way of transfering from one place to another. It just helps him be unable to die, and his soul then possesses the body thats wearing it, kinda like a demonic possession. It's the old persons body but a different being is operating it. Then that body does in fact become Jack, not JUST his mask. If he operated inside his mask then it would be more like Lord Voldemourt from Harry Potter. In the first movie/book Voldemourt's soul is attached to another person but the other individual still controls his body.