how to set up iTunes for playback so that track does not automatically follow track
This may be possible with a newer iTunes but is not possible in my iTunes (version 7.5). I would also suggest checking the Dougscripts web site for one called "play just this one" which plays only the selected track.
Alternatively, display the files in Finder and open them with Quicktime Player. A window will be opened for each file you open and let you play them one by one.
how to burn a cd so that the specified gap between tracks is neither 'none' nor a number of seconds, but no continuous playing track after track.
As I said, this is not possible. There is nothing you can do to the CD itself to do this. It is not something that is a feature of the CD, it is done purely by the device you use to play the CD and all I have used do continuous playback. The only thing you can change about the CD is content, the order, and the gap between tracks.