dga: "Charlie I watched the video. I didn't see anything that addressed controlling parts of the song, repeats, shortening a song by dropping a verse etc in Ableton. I've seen DJs use a controller to do this a lot. I wonder what they are using."
Ableton can be operated by computer keyboard, midi keyboard, footswitch, midi controller. Remote switching can be programmed onto a channel within a project.
Ableton can process each of the control options you list above.