Most mums are getting close to booting their babies by that age anyways. The bond is NOT developing further IMO/EYes it’s 5 weeks old.
I personally would put blacky in a broody breaker (dog kennel, etc) still in sight of the other 2.. and break broodyness sooner next time.. maybe for both of them.
If they can't successfully hatch more than a single chick.. maybe they shouldn't be allowed to sit especially that long.. it's clearly disrupting the pecking order and causing stress for everyone.. including you.
If she's going to roost and not the nest box then she's not broody.. she being a beeyotch.. set her up for daytime timeout still... we call it look but don't touch. It may take several days.This is what I’m thinking of doing, but I’ll have to wait until nightfall to get her from the roost. I think she senses what up and she’s not letting me get close to her.
Pin less peepers if she continues to be aggressive after the time out and reintegration.. sounds like a broken flock to me.. probably due to the broodiness that lasted too long and overlapped.. extending the time of disconnect.
Just curios what state or country are you in that has feral roosters?
Hope you find a peaceful resolution!