Hi, welcome to the forum. Glad you found us. I know it is easy to say and hard to do but try to relax some, you will get through this.
they ended up plucking so many feathers off of her.
I did not see where you are located, north or south of the equator. Are you sure the other hens were actually plucking feathers off of her or is it the molt. If you are in the northern hemisphere it's normal for mature chickens to drop their feathers in the fall/winter and replace them. For some that is a really slow process, you can't tell without a close examination that they are molting but others drop their feathers in a hurry and can look quite bare. When they are molting you see a lot of feathers flying around. It is pretty normal for chickens to eat feathers flying around, especially the little fluffy ones. Did you actually see plucking? It can and does happen, but sometimes people see them eating feathers flying around and assume plucking.
he is 5 months old
That may be part of the problem. He is not a rooster, he is still an immature cockerel. Don't think of him so much as a mature male but as a teenager hyped up on hormones, with no self-control, and no parental control. Also, he often has not yet learned good technique. He can be rough.
He calls them when i bring fresh veggies out to the yard, dances for them, and balances well on them, but he really grabs them hard and pulls on their combs. He is a very randy rooster
In spite of what I just said this doesn't sound that bad. I'll copy something I wrote about mating behaviors and why they go through them. It might help. This is an idealized version, not all adults go through this exactly like this, there are always variations. The "head grab" is an essential part of mating.
An immature cockerel especially can be very randy. It's in their nature and their hormones.
Typical mating behavior between mature consenting adults.
The rooster dances for a specific hen. He lowers one wing and sort of circles her. This signals his intent.
The hen squats. This gets her body onto the ground so the rooster’s weight goes into the ground through her entire body and not just her legs. That way she can support a much heavier rooster without hurting her joints.
The rooster hops on and grabs the back of her head. The head grab helps him get in the right position to hit the target and helps him to keep his balance, but its major purpose is to tell the hen to raise her tail out of the way to expose the target. A mating will not be successful if she does not raise her tail and expose the target. The head grab is necessary.
The rooster touches vents and hops off. This may be over in the blink of an eye or it may take a few seconds. But when this is over the rooster’s part is done.
The hen then stands up, fluffs up, and shakes. This fluffy shake gets the sperm into a special container inside the hen near where the egg starts its internal journey through her internal egg making factory.
Is this behavior normal??
I think it is highly possible something else is going on. The mating act is not always about fertilizing eggs, especially with immature cockerels. You'll see that behavior even when they are with immature pullets not yet laying. In the mating act the one on bottom is accepting the dominance of the one on top, either willingly or by force. If your hens don't accept his dominance it can be by force. If some accept him and some don't he can channel violence toward the ones that don't. Older roosters usually manage by the force of the personality, immature cockerels often have to resort to force.
I don't know what is going on with yours. It could be different things or a combination of things. So what can you do.
If you can get through this phase things usually mellow out when they all mature. Not always but usually. If this behavior is only between those two you could isolate one of them until he matures, say another 2 months before you try again. I'd isolate him, integrating him later will probably be easier than reintegrating her.
If you can stand it you can try to let them go and see if they can work it out with no one really hurt. They often do but if violence is involved it can be dangerous. If he is making her barebacked or removing feathers from the back of her head she can be injured. At 5 months he should not have spurs yet but his beak and claws are quite sharp. I would not touch the beak but there might be a benefit to taking the sharp points off of his claws.
How badly do you want that boy? If he is causing problems solve for the peace of the overall flock and get rid of him.
This type of behavior is pretty normal for an immature cockerel. That does not mean it is always acceptable,
they ended up plucking so many feathers off of her.
I did not see where you are located, north or south of the equator. Are you sure the other hens were actually plucking feathers off of her or is it the molt. If you are in the northern hemisphere it's normal for mature chickens to drop their feathers in the fall/winter and replace them. For some that is a really slow process, you can't tell without a close examination that they are molting but others drop their feathers in a hurry and can look quite bare. When they are molting you see a lot of feathers flying around. It is pretty normal for chickens to eat feathers flying around, especially the little fluffy ones. Did you actually see plucking? It can and does happen, but sometimes people see them eating feathers flying around and assume plucking.
he is 5 months old
That may be part of the problem. He is not a rooster, he is still an immature cockerel. Don't think of him so much as a mature male but as a teenager hyped up on hormones, with no self-control, and no parental control. Also, he often has not yet learned good technique. He can be rough.
He calls them when i bring fresh veggies out to the yard, dances for them, and balances well on them, but he really grabs them hard and pulls on their combs. He is a very randy rooster
In spite of what I just said this doesn't sound that bad. I'll copy something I wrote about mating behaviors and why they go through them. It might help. This is an idealized version, not all adults go through this exactly like this, there are always variations. The "head grab" is an essential part of mating.
An immature cockerel especially can be very randy. It's in their nature and their hormones.
Typical mating behavior between mature consenting adults.
The rooster dances for a specific hen. He lowers one wing and sort of circles her. This signals his intent.
The hen squats. This gets her body onto the ground so the rooster’s weight goes into the ground through her entire body and not just her legs. That way she can support a much heavier rooster without hurting her joints.
The rooster hops on and grabs the back of her head. The head grab helps him get in the right position to hit the target and helps him to keep his balance, but its major purpose is to tell the hen to raise her tail out of the way to expose the target. A mating will not be successful if she does not raise her tail and expose the target. The head grab is necessary.
The rooster touches vents and hops off. This may be over in the blink of an eye or it may take a few seconds. But when this is over the rooster’s part is done.
The hen then stands up, fluffs up, and shakes. This fluffy shake gets the sperm into a special container inside the hen near where the egg starts its internal journey through her internal egg making factory.
Is this behavior normal??
I think it is highly possible something else is going on. The mating act is not always about fertilizing eggs, especially with immature cockerels. You'll see that behavior even when they are with immature pullets not yet laying. In the mating act the one on bottom is accepting the dominance of the one on top, either willingly or by force. If your hens don't accept his dominance it can be by force. If some accept him and some don't he can channel violence toward the ones that don't. Older roosters usually manage by the force of the personality, immature cockerels often have to resort to force.
I don't know what is going on with yours. It could be different things or a combination of things. So what can you do.
If you can get through this phase things usually mellow out when they all mature. Not always but usually. If this behavior is only between those two you could isolate one of them until he matures, say another 2 months before you try again. I'd isolate him, integrating him later will probably be easier than reintegrating her.
If you can stand it you can try to let them go and see if they can work it out with no one really hurt. They often do but if violence is involved it can be dangerous. If he is making her barebacked or removing feathers from the back of her head she can be injured. At 5 months he should not have spurs yet but his beak and claws are quite sharp. I would not touch the beak but there might be a benefit to taking the sharp points off of his claws.
How badly do you want that boy? If he is causing problems solve for the peace of the overall flock and get rid of him.
This type of behavior is pretty normal for an immature cockerel. That does not mean it is always acceptable,
. She is missing feather off of her head, but it could be both molt and the cockerel. I moved her in with my 6 to 7 week old babies that I got, and is doing MUCH better. She enjoys being around the babies a lot, but doesnt have access outside. I could get rid of him, but he has a pretty good nature other than the aggressive like mating. The other hens are actually accepting him better than the one he has been favoring. They get a little upset with him when he wants to mate multiple times, and will run from him, other than that they mate well. They were put through the shock of being separated from the other chickens they had, and not having their norm. Im hoping it will sort out. Id like to have him for his protection from predators as i live in the country, but they do have a secure pen that has never had any predator issues in the past, per the previous home owner.
getting chickens in the winter is especially hard, because cold temperatures can bring on unforeseen troubles. But then again, summer chicken-keeping is going to be a breeze for you! They are lucky to have a owner who care so much for them 
