I was just using random numbers re the bitrates, take no notice, I was just trying to get the concept across to anyone who may be reading
I would actually go with a higher minimum bitrate, even on really still scenes, if it's too low you get wierdness with film based material because of flutter on non pin registered film.
Anyhoo, it will look a lot better with the higher bitrate that dual layer allows.
I would crop the top and bottom to remove any closed captioning or subtitling, and add them into the DVD subtitles to maximise your video quality.
If you mean extract the closed caption data from line 21 of the NTSC signal, then the SCC tools package will do that.
You can get it here http://www.geocities.com/mcpoodle43/SCC_TOOLS/DOCS/SCC_TOOLS.HTML