If you feel like your son's behavior is disrupting the entire family, and his outbursts are out of proportion for what it is he wants, I would highly recommend a professional evaluate the situation.... meaning a Child Psychologist.
A good Child Psychologist will get a lot of information from you, from his teachers/caregivers, meet with your son, then compile all the info, and give a recommendation.
Sometimes, if the child is in need of medication or intense therapy, the psychologist may recommend he see a Child Psychiatrist - - it just really depends on the situation, family history and his environment.
I understand how difficult it is to parent a child like this - - most people blame it on bad parenting, but that's often not the case. So hang in there and seek out a really good Child Psychologist to meet with you guys and get to the root of your son's behavior.
Maybe this particular school environment isn't the right "fit" for your son.
I would do some research of other schools in your area - maybe a smaller school, a Charter type school ? Charter schools often have smaller class sizes, and will have different learning styles (like more hands-on activities).
Not all kids fit in the typical classroom setting, and I think exploring your school options would be a good idea.
I urge you to talk to your son's pediatrician about his behaviors.
These types of outbursts do not just 'go away' - your son needs help, and he needs you to help him get it.
I'm sure he doesn't understand why he is acting out, its probably very scary for him. As your son gets older and older, his violence will most likely increase, so getting a hold on what is going on now, is imperative.
The pediatrician is a good place to start, then he may refer you to a Child Psychologist for evaluation.
In my opinion, this little 9-year old has had a chaotic few years of her life. Parents splitting up, mom remarries, has a step-father, gets molested, doesn't see Dad regularly - and frankly who knows what else has happened at her mom's house......
I would highly, highly suggest this young girl get into some good counseling with a professional who is smart and understands young girls who have experienced trauma - not your "run of the mill counselor", but a Child Psychologist who specifically works with young children.
When I hear situations like these, it reminds me of my youngest daughter.
The very best information I can offer you is to find a smart, qualified Child Psychologist and/or Child Psychiatrist to do a thorough evaluation on her. Mind you, a thorough evaluation should not just be done in one visit, but over a course of a few visits, with a ton of paper work for you and her teachers to fill out.
Know what is behind your daughters behaviors is extremely important, and it is most likely more complex than just reading books and parenting.
I'm sure your daughter is not happy with the way she is, but doesn't know how to change - probably doesn't know what is driving her mood / behaviors.
But as I mentioned above, a top notch Dr. is key here!