That was a soap opera filmed back in the times where spankings were something that happened. They were also used as a substitute for sex (see John Wayne films). I'll have to watch / listen to them for the spanking references. I did try watching them years ago (on VHS) but the melodrama was so very melo that I couldn't finish those VHS tapes.
There are other Dark Shadows things out there. There were a couple of movies made back then - with no spankings. I've seen both.
It was relaunched as a Johnny Depp movie in 2012. Chloƫ Grace Moretz (Hit Girl from Kick Ass) was 14 / 15 when she played a 15-year-old character, a teenage girl who wanted to move from backwater Maine to NYC. Alas, it wasn't the late 60s / early 70s, so there was not any references to spanking her (just being locked in her room). There wasn't even spanking references towards her younger brother. That said, it's an interesting movie to watch. Johnny Depp playing a vampire from the 18th century interacting with Hippies... Depp's character commenting how ugly a woman hired to sing at a party is - and Alice isn't even a Cooper. Yes, Alice Cooper plays the Ballad of Dwight Fry, with Chloƫ Grace Moretz doing the little girl intro. And the four surviving stars from the original made cameos during the party scene.
See
https://www.youtube.com/watch?v=aJ-6ZqMNAo8 for the song.
There were Golden Key comics made about the show. Dan Ross (writing with one of many pen names) wrote many Dark Shadows novels. I meet him at a con and he said that the series was very successful / profitable.
After the show ended a company called Big Finish started making audio dramas set there, the same way they made audio dramas of Doctor Who. Often they had the original actors reading their characters' part, but those actors have mostly died off. See
https://www.bigfinish.com/hubs/v/dark-shadows for more.
The Dark Shadows fan community is still going strong across the generations.