When I've done video storyboarding, I used one column for the audio, and one column for the video. Also, I tend to use an overall time counter, rather than duration (e.g. 5 minutes into the video, 6 minutes into the video, etc.)
These ideas make a lot of sense. Particularly the time counter...
Yeah, I reckon a closer relationship to film/video story boarding would be better. I prefer the film production process for its relative simplicity. It involves 3 stages of preparation - the treatment, then the script and finally the storyboard. When the storyboard happens, it is simply a comic strip with a frame of descriptive text (that might include timings etc). Anything needing more complicated description is written up in the script and treatment, and for interactive non linear developments, its a matter of developing lots of storyboards.
I think what you have here is a combination of the instructional designer and film maker storyboard. The cell that you have for icons.. I think it should be more dominant, and should be used to illustrate the story more (rather than iconise it). To demonstrate this, I think it would be a matter of drawing the story frame and replacing the icon with the scan of the drawing.