I first saw Jonathan Frid on Dark Shadows (Original Series, not the remake); from the Wayback Machine: https://web.archive.org/details/www.darkshadows.com as the site is no longer available. As i was logging into Find-A-Grave earlier today, his memorial showed with a note about today was his birthday: https://www.findagrave.com/memorial/88753658/jonathan-frid. He used to have his own site – http://www.jonathanfrid.com/, but when I went there today, it had been transformed into something else which is why I didn’t link to it. You can get a good sense of the old site on the Wayback Machine: https://web.archive.org/web/20120503195927/http://jonathanfrid.com/.
You can see other things he appeared in on IMDB: https://www.imdb.com/name/nm0294847/?ref_=nv_sr_1. It doesn’t look like IMDB includes his theater work, other than in his bio: https://www.imdb.com/name/nm0294847/bio?ref_=nm_ov_bio_sm.
I used to own Dark Shadows Complete Series on DVD: https://www.amazon.com/Dark-Shadows-Complete-Original-Deluxe/dp/B007PZ6SYK (not an affiliate link) – a good price at $299.99 as its regular price tends to be a fair amount over $300.
It’s a pretty campy show as they had a very small budget. You may see the string holding the fake bat. When they filmed it, they did a rehearsal before filming it. When they filmed it, it tended to be a one-shot deal. Unlike today where you got multiple tries, the show’s budget was so low that you only got one take.