First of all, I totally understand your situation. I lived with a violent child for years. What I will say may seem harsh but is said to help and not to hurt or judge.
The violence MUST STOP. No matter what else is going on, the violence absolutely must be stopped. How long has the hitting been going on? Is it a long term, since he was little problem? Did it start suddenly or just gradually build up? Is it new, since he started on medications or on a certain medication?
I looked at your medication list. Is he taking 4 medications? If so, what is the fourth? Citalopram and Celexa are the same medication. Some of the medications he is on may cause or contribute to aggression. Vyvanse is a stimulant and those can certainly contribute to aggression. Some people, especially children, become violent on antidepressants. Did the aggression start before or after either of these medications was started? Did the amount/level/type of aggression or his choice of targets change after he started taking either medication?
Abilify is an atypical antipsychotic and should help curb the aggression and help with depression. What impact did taking abilify have on his violence? We had a lot of luck with risperdal (risperidone) for quite a long time with my son. If the abilify isn't helping, then maybe trying risperdal or seroquel or another atyp antipsychotic could help.
WHo oversees his medications? Why is each prescribed? Has anyone ever thought he could be bipolar? I ask this NOT because I think he has bipolar, but because children with bipolar present VERY differently than adults and because medications can cause havoc in a person with bipolar. You might check The Balanced Mind foundation (used to be the Child and Adolescent Bipolar foudnation) for info to learn more about bipolar. Or get a copy of The Bipolar Child by Papalous to learn more. There is an online tool to see if your child might have bipolar that is called the Child Bipolar Questionaire or CBQ that you can get via this link:
http://www.jbrf.org/cbq/index.html . It was designed with input from the author of the Bipolar Child and does NOT tell you that yes he is or no he isn't bipolar. It just gives you a tool to take to his doctors to help evaluate what is going on.
I am NOT saying I think he is bipolar. I am saying that I think maybe it would help to think about it. I do think that bipolar is overdx'd in kids, but that doesn't mean that some kids don't have it.
The book What Your Explosive Child is Trying to Tell You by Riley is a must. You have to know why he is exploding before anythign will change. You also have to take big steps to keep everyone safe. The violence is not a new behavior from the sounds of things. You MUST make it the MAJOR priority - even more important than school, in my opinion. He can't learn if he can't be around people because he keeps hurting them. Sooner or later it will be aimed at others and then you have some huge problems.
Sit down an write a safety plan. Who does what, goes where, etc... when difficult child is violent. Your daughter must especially be protected. This is going to sound really mean, but I seriously doubt you have any idea of how violent he is to her. Chances are that when you can't see or it is late at night, he is taking his anger out on her. She isn't going to open up until he is out of the home or has been safe for several MONTHS. If she tells he will hurt her worse. She may also think he is violent because he is sick so he can't help it.
I KNOW HOW THIS HURTS TO THINK ABOUT. I really do. My son hurt his sister and I for years. husband and I spent over 5 YEARS never leaving them in a room together with-o adult supervision. If we went to potty we took the same sex child to the bathroom with us. I would have Jess stand in the shower or tub so I had a little privacy and husband would do the same with Wiz. If we didn't, Jess was bruised or bleeding when we returned to the room. We were terrified and NO ONE really believed us. not for a long time. Then one night the cat got me up and insisted I follow her. She led me to my daughter's room. Wiz was strangling her. She was sound asleep until he came in and woke her up with his hands around her throat. We were terrified and so angry at him. I was truly afraid that if I paid any attentiont o him at that moment that I would kill him. Not "kill him" as in he would be in trouble. Kill him as in he would never breathe or move or do anything ever again and I would go to prison until I could kill myself. It took about a split second to realize that I was not safe to be around him right then. I took care of my daughter and screamed my husband awake to come and take care of Wiz. thank you was with Jess and I.
It was awful. My son ended up spending 4 months in a psychiatric hospital and my daughter got a LOT of therapy. We took her to the pediatrician the next morning after the incident and the doctor reported us to CPS - I asked her to. I knew it had to be reported and I wanted their help to get all of us the help we needed.
My son was 12 at the time. Not much older than your difficult child. It took three months for my daughter to be able to sleep through the night in her own bed. She spent a lot of nights sleeping with husband and I because she was so scared at night.
I can't write much more now, but there IS hope and help. Right now my son is 20 and in college wtih straight As, has held a job for 4+ yrs, lives with my parents about 15 min away and is a loving son and brother and has a great relationship with his siblings. I will write more later but have to go now.
PLEASE contact the domestic violence center in your area and get an intake appointment. This IS DV and they can help. they may or may not have much experience with kids who hit parents, but they can still help you. I got a lot of hel pfrom our dv center.