Sorry for the late reply. For future reference, if you have a question off-season you'll probably have better luck emailing us at fmv (at) fanime.com. We don't check these forums daily in the off-season.
The easy answer is, yes, all the finalist videos are spliced together into one file. It's easier for the coordinators and the staff & volunteers who run the program. The show is rendered out at 1280x720. Smaller, 4:3 videos aren't stretched but just fill up the space they naturally would and remain 4:3. This is pretty practice common for AMV competitions.
As of 2014 there were no official rules that videos be anime or VG-sourced only, but that may be subject to change in 2015. The rules aren't decided yet and some things may be changing. You can expect the new rules to go up sometime early next year. Submitting your video won't be possible until then, so there's no rush to get your video formatted for our show just yet.