[spkguitar]

Protools treats the 8 ADAT and 2 s/pdif inputs just like any other input, so yes they would be separate files (as long as you set them up that way). A total of 18 inputs is possible at a time.

Doing what you want to do with the separate computer is definitely possible (as long as you like the sounds you're getting with that setup already). Personally, I think it's too much work, but that's just me. I used to do this with a motu interface, my old 001 and Cakewalk Sonar on a separate PC, but I gave up on it because I thought it was a pain, but YMMV.

You shouldn't need any extra software; you would just connect the two PCs via MIDI and set one program to send MMC and one to receive. Check the manuals for the specifics with each software.