Add that inside a home, the IP is again behind a NAT because the whole family is using the wi-fi. Including people who drop by to visit you, to have a dinner, to watch a game.
One IP per person really doesn't hold.
One IP per person really doesn't hold.
Edit: this is incorrect apparently.
I don't have AT&T so I didn't pay much attention to the details. One possible approach: https://github.com/jaysoffian/eap_proxy
It has the same affect on you as your neighbor does.
Bandwidth would be unaffected. Or more exactly, on WiFi (but not Ethernet): as affected as if your close neighbor used that amount (since WiFi itself has limited bandwidth). The connection from the router to the cable modem has lots of headroom, so that would be unaffected, as would wired connections.