If what I’ve read and remember is correct, a chick with Barred blood will produce a spot on its head if male. Please correct me if I’m wrong. At this point I’d be very tickled to be wrong.
You're partly right and wrong.
When chicks have a barred MOTHER and a not-barred FATHER, they can be sexed by which ones have a dot on their head.
But a barred FATHER can pass the barring (and the head-dot) to his daughters as well as his sons. Since your rooster is a mix, with only one barred parent, then he can pass barring to about half of his chicks. (And some of the others may have gotten it from their mothers, but you won't know which are which.)
Also, purebred Barred Rock chicks can have dots on the heads in both genders.
So don't give up on all those dotted-head fluffy chicks yet. If you've got 7 with dots, I'll predict, um, 2 pullets in there (because I always assume less than half will be the gender I really want.)