Julian,
I believe that what is written on page 15 is a mistake, because the natural sea salt is unrefined salt, so my guess is he is talking about using sea vegetables to supplement refined or table salt.
Crude salt is also sea salt unless it was mined inland, like rock salt.
I don't know about scallion miso but maybe you could try Dandelion-Leek Miso:
(
http://www.southrivermiso.com/ourproducts/special.html )
Is this the movie you are talking about?:
Himalaya - l'enfance d'un chef (1999)
(
http://us.imdb.com/Title?0210727 )
Thank you, very much.
With warm regards, love, and peace,
Bruce Paine