That Sandy Dennis movie was called Something Evil and directed by Steven Spielberg. He did it shortly after the much-ballyhooed Duel (which I never saw, the subject matter sounded intensely boring to me). Darren McGavin was in it, and so was Johnnie Whitaker (who was on Family Affair, the Sebastian Cabot/Brian Keith vehicle).
I remember it vividly too, but haven't seen it since the early 70s.
I'm afraid the use of the pentagram-on-the-floor in the Summer of 1970 sequence wasn't any more accurate than the use of it we just saw, but the incantation was fun.
It was wild that they were doing all this stuff in 1969/1970. In Maryland, at least, this stuff was very exotic. Every week I would go to the library for more books to tell me about what I was seeing on Dark Shadows. It had such an impact upon my imagination.
Gothick