1) This box is designed to fit behind your TV. I does require a wall outlet but the presumption is that one is there for the TV.
2) We don't have any plans currently for a Surround Sound version of this. Our thinking is that most people will wire their theatre system with speaker wires as the surround channels normally do not have AC nearby. This said an amp box like you are mentioning in 3) could have a lot of benefit for some surround channel installations.
3) This is a likely future product for this project for the reasons you mentioned.
4) The price point of the combined speaker/amp combo will be less than the separates.