I can help with your Apple TV problem.
While the Apple TV can probably work like an access point, it would not work very well. One could trying finding out what binary file the iPhone 4 uses to make a WiFi hotspot and transfer it over to the Apple TV. Once the proper initialization commands have been found, one would have to hope that it is able to take the Ethernet connection and use that instead of the cellular connection is would be using on an iPhone. There are also many other things it could need, such as the proper lib caches and WiFi chipset support. Both of which a 3Gs and iPod Touch 4G running 4.3.X lack.