Hello Venus,
I hope you are able to find something. At one point, I was very interested (obsessed?) in his whole story and records of Darrell. A few years ago, I checked that website and others for listings of artists appearing. I looked at each and every week of the Bandstand shows!!
I didn't find any mention of Darrell.
I came to the conclusion that if he did appear, it may have been some sort of "walk-on" part, just to say hello and mention his next release. So, perhaps he was on after Revilot 201 was released and before 203 or one of his other releases came out. He didn't have that many. Possibly even the release of one of the album's. I think I read somewhere that he may not have been the most approachable character!
Good luck,
Kev Bod
(p.s. - I did like the footage of Broken Heart Attack you came up with)