Keynote video pausing/playing
The easiest way I can think of would be to actually do it as multiple videos and stills.  Have the first video play and then go to a still of the last frame.  The next would be the next video clip followed by the still.  Continue doing that for the length of it.  Not sure if it works like that in Keynote or not, but that's how I'd do it in any of my sequencing/presentation packages.