Hi. Welcome to the forum. Glad you joined but wish it were under better circumstances.
It sounds like you've done about everything you reasonably can. Two and then three weeks of look but don't touch, a big run with some clutter, separate feeding and water stations. You separated out some of the troublemakers for a while. How did the CQ's act with the chicks with the RIR's gone? Were they still vicious and hunting down the chicks? Sometimes when you remove the instigators the flock dynamics change.
It's pretty normal for my mature hens to outrank immature pullets in the pecking order and be willing to enforce those pecking order rights. But that's when the immature invade their personal space in the coop, in the run, or on the roosts. It usually doesn't take long at all for my immature ones to learn to avoid the adults and form a sub-flock until they mature enough to join the pecking order. With mine that's usually about when they start to lay.
What is somewhat unusual is that yours hunt down the juveniles when they try to avoid the adults. I've seen that behavior when they are settling down on the roosts at night, one hen left her normal area of the roosts to go attack some juveniles on the far end of the roosts. But that was just one hen, not several of then, only a few times, and they were fine during the day. Others on here have reported that kind of behavior with their flocks with hens of many different breeds. Most of those come when room is limited, you should have plenty of room. I don't know how big your coop actually is but since this happens in the run I don't think it is a space issue. And it sounds like it could be several of your adults, four out of six is unusual. But maybe just one or to are instigators. From my experience this should have gone a lot better for you than it has.
So what can you do? They seem to tolerate the other EE's. You could keep those pullets separated until half of them start to lay. They may be accepted into the flock then.
You can try isolating the RIR's and see how the CQ's react when you try to integrate. They may be OK, they may be part of the problem. At least that would give you some guidance with them. If things are peaceful you can try reintroducing the RIR's after at least a week. Two weeks wouldn't be bad. See how they behave.
Is it all the young ones they go after or only a select one or two? Are you sure they are all pullets and you don't have a cockerel in with them? Sometimes hens will be especially brutal to a young cockerel though I haven't seen that be this bad. I've also seen one chicken take an intense personal dislike toward another, bad enough to want to kill them. With that many hens involved it doesn't sound like that but who knows. Also, sometimes a flock will try to drive a sick, injured, or really weak member out of the flock. It's an instinctive survival technique, a weak chicken might attract predators to the flock. Again, if it is more than one or two of the young ones this is not it. I'm just trying to cover all the bases.
I try to solve these issues for the peace of my overall flock, not for one chicken. One reason I keep chickens is for meat so I have an easy solution for troublemakers. Maybe that's part of why I have a pretty peaceful flock. This doesn't mean you have to eat them, you can permanently isolate them, sell them, or give them away if, after reasonable efforts on your part, they are not reasonable. To me, there are too many good hens out there to put up with a bad one.
Good luck. It sounds like you haven't had much of that with these chickens. And once again,
