Hi, C.
My heart goes out to you, I'm in a similar position with my 15 (soon to be 16) yr old son. His father is alive and well, but very absent. His little brother is 5 and on the hyperactive side. I have gone through a lot of extremes with him over the last 14 months. We finally hit a wall when he was failing two subjects last school year because he was sneaking out of the house during the night. Over the summer I had to answer to the Sherriffs Dept., OCS, they all reccommended Rosenblums Mental Health unit in Hammond Louisiana. They decided his behavior was a "danger" and transported him to the Emergency at Childrens Hospital and he was finally admitted to the Childrens Hospital Mental Unit to address his issues. They kept him for 2 weeks and addressed his anger and helped him learn new ways to deal with it. They put him on some medicine which is helping alot: Resperdone, it helps him steer his emotions instead of them steering his actions. Most of my son's aggression is abating, but he still has a ways to go on the attitude .... we have a pathways counselor coming to our house twice a week to continue teaching him healthy ways to communicate with family members, and family members how to cope in a positive way. I strongly suggest you get him checked out before his anger escalates. If you are near Hammond, the Rosenblum Clinic is an excellent resource.
When dealing with the home environment, usually the younger brother just wants his attention and I try to remind the young one not to be physical unless he wants his brother to be physical and someone might get hurt. Then I remind Big Brother that his Little Brother loves him and wants to spend time with him, then try to suggest something they both enjoy like a puzzle or frisbee, maybe take the dogs on a walk. As far as the computer and tv, I would make up a time chart to help everyone get along, and keep the peace. They make a "Nanny Program" that monitors computer time. You can set up different times for different kids with passwords. Perhaps reward the younger ones for good behavior and let them set a good example, give them tv or computer "bonus time" while you are home, maybe special time with you, and maybe take away alotted time if violent or disobedient. Maybe you could get a family member or friend to step in after school until you get home to keep an eye on the kids and see to it that they follow the new rules. I've also seen camera monitoring systems that you can see on your cellphone or computer at work. Also, try to spend time with just him and see if you can get him to talk about his feelings, just remember not to be pushy, its a really hard age, boys feel things intensely and feel they are all grown up at that age.
Best of luck! Hang in there.