Although it's not really an answer to the questions you raise, Norman Lebrecht's (frequently fact-wobbly) blog
Slipped Disk had a feature about Previn today:
http://slippedisc.com/2015/10/andre-previn-my-problem-is-i-just-dont-rewrite/Quite apart from his work on the concert platform, Previn is probably best-known as one of the generation of "expert explainers" of the late 1960s and 1970s - true experts in their field who were ready to share their expertise with the public, in a non-patronising way. They realised the potential the medium of television had in reaching-out to new audiences, who were keen to know more... provided it wasn't presented in the "Auntie knows best" castor-oil style that had gone before ;)
Probably the earliest pioneer in this way of presenting provoking ideas about culture was the legendary John Berger ("Ways Of Seeing"). If nothing else, Previn picked up Berger's idea of colourfully outrageous fashion shirts (!) for the LSO :)
Worth remembering too that Previn has always maintained his highly-respected parallel jazz career.