1) One gold account will cover every account on that console so long as it's set to be that main account's home console, which is the case by default unless you change it.
2) You'll have to buy a charge kit, or use your own rechargeable batteries
3) Nothing I can think of. However, if you and your family/cousins/etc all buy digital, you could ask one of them to make your Xbox their home console, and that way you can download and play any games they own for free. This can potentially save you tons of money on games.
4) Doesn't really matter since you can supplement your Xbox with USB 3.0 compatible external drive whenever you should run out of space. That said, more space doesn't hurt so you might as well go for the full TB.
5) I'm not really up to date on this
6) Not gonna list all that. Google is your friend. It does pretty much everything you'd expect.
