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I'm not real clear on your set-up. Is the coop 12 x 5 or is that just the run under it? And do they get access to the yard since the rooster leaves the yard? Space is important on how they act. If your space is tight, then you are more likely to have problems.
Hens and roosters have been living together for thousands of years. They have methods worked out for new ones growing up in the flock. They are living animals. Sometimes bad things happen, but usually bad things don't happen. Their ways may look rough to you, but they are chickens, not people.
Age as well as space also plays a big part in how they act. Chickens go through adolescence. Hormones run wild and they don’t have the maturity to control them. Most people on this forum think only about the rooster, but those pullets go through the hormonal phase too. You don’t mention how old they all are, but it sure sounds like they are pretty young.
It’s possible that as your rooster and the pullets mature, mating will get rough. They are inexperienced and don’t necessarily have the technique down. The risk from this is that the pullets lose enough feathers that the rooster can rip the skin in them during the mating act. Remember that chickens have been going through this every year for thousands of years. Some feather loss is perfectly normal. Will that rooster rip them to shreds? It’s possible but not likely, just as it is possible you will have an accident the next time you get in a car, but not likely. Don’t obsess over it.
I suspect your one hen is older than the four. Mature chickens naturally outrank less mature chickens in the pecking order and are often bullies about it. What your chicken is doing with keeping them away from the food and water sounds typical for this behavior. When your younger ones mature to the point they can establish their position in the pecking order, this behavior will stop. When will this happen? It depends on how fast they mature. This behavior is almost always the hens. A dominant rooster, especially a mature dominant rooster, practically never behaves this way. Immature non-dominant roosters often do, but not a dominant one.
You are right. You do not need a rooster for eggs. The only reason you need a rooster is to make the eggs fertile if you wish to hatch eggs. If space is tight or you don’t want to deal with him, it won’t hurt to get rid of him. With a flock of all hens and no rooster, one hen often takes on certain roles of the rooster. She may go through the mating ritual with the other hens just to show she is dominant. She may break up fights, keep watch for predators, and in general do what a rooster does to maintain peace and order in his flock. But this takes some maturity on her part too.
I’m not sure how your older pullet will react if you remove the rooster. She may become more of a bully or she may decide she wants the company and merge with the others. She may mostly hang out alone until they mature enough to suit her. She will adjust. You won’t need to schedule a visit or a house call from Dr. Phil to sort out her psyche. The social order in the flock will change if you remove the rooster, but they will sort it out. Chicken flocks have been doing that for thousands of years.