1. You already realize you need a PSU.
2. Sure. use a USB webcam style of camera.
3. You'll have to look for miniPCI offerings. There are also USB sound & video adapters that may work for you, as well.
6. I believe it would. You can also use the PC as a bluetooth headset.
One thing I will say.
You are likely to be disappointed in the performance of that VIA NanoITX board.