For what it's worth, here's the Wikipedia entry on the concept of canon as being discussed here:
http://en.wikipedia.org/wiki/Canon_(fiction)
For Star Trek, they give a definition that contrasts with the one I have given for DS. I feel strongly that canon for Original Series DS consists of the episodes as aired, full stop. This is the case even though I really dislike some decisions that were made in canon about character fates, notably Victoria Winters' "final" fate. (Dale Clark's first DS fan novel was written specifically to give an alteration to this canon, which has disturbed so many fans over the years.) Another interesting example of this is in the 1980s TV series Beauty and the Beast, where TPTB provided an ending that many (perhaps most) fans regarded as outright character rape. I think this may have been the first instance where fannish writers provided an alternate season of episodes to what had been aired, a practice that has since become popular in Net fandom with many canceled series.
Cousin Barnabas, Roger Davis's "performances" as Jeff Clark in 1968 definitely rate as among the most hair-grippingly awful (lol) material he did on the show, so I feel your pain.
For a lot of us Ancient Blood fans (viewers during the time of the original airing), the 1968 period has its own nostalgic overlay because it was during this time that DS really hit big in mass media coverage and national awareness. Which was why the era was recalled by some cast members as "that year of insanity." lol!
G.