Welcome to the board. It is wonderful to have you join us, but I am so sorry that you had to come and find us. It must be incredibly difficult to deal with your stepdaughter for such long stretches without your husband at home. You are a strong, brave and wonderful mom for doing this.
What was your stepdaughter's very early life like? Did her mother use alcohol or drugs during the pregnancy? Did your stepdaughter get abused or neglected during that time, especially during the first 3 years of life? This can have a HUGE impact on a child. How is she with animals? Has she ever hurt one? Do you feel comfortable leaving her around them?
You might want to do some research into Reactive Attachment Disorder. This happens when a child is abused or neglected in the first 3 years of life. (I am NOT accusing your husband of this. If he was on the road while he was with her mother, it could EASILY have been hidden. If they were not together, it would be even easier to hide.)The child is unable to form attachments to other people. It is terribly sad and the in the worst cases, children can be incredibly dangerous. There are other forms of attachment disorder that are also possible. You might want to do research on this.
If she was exposed to alcohol or drugs in utero, she may have problems because of that. It is possible to have a normal appearance and to look like you have not been impacted by your mother's substance abuse but to still have serious problems. It might play a role in her problems.
As far as what to do, there are a lot of things to try. The first thing I would suggest is for you to write a Parent Report. It is a report all about your stepdaughter. All the good and bad. Parents here before me created the outline and it really helps keep things organized. It also helps you communicate effectively with the various professionals that may be needed to help her and to keep you all as safe as possible. You can click on the link in my signature (at the bottom of this post) to find the thread about the Parent Report.
One thing I would suggest right off the bat is to remove her lamp. If she is misusing it to try to set the house on fire, she should not have it. If you don't have a fixture on the ceiling, consider getting on of the newer fluorescent bulbs for the fixture that does not get hot. Or have her depend on sunlight for light in her room. It would be a logical consequence for misusing her lamp.
Another things is to consider putting a security camera up inside your house to see what she does when she gets up in the night. Does she leave her room (do NOT put a camera in her room)? Does she do anything you need to worry about now? How often does she get up? Where does she go? If she is up often, you might consider a sleep study to figure out why. Sleep is crucial for health and proper growth. If she isn't sleeping enough, it could cause many problems. I would NOT let her know that there is a camera in the house, at least at first.
A second benefit of having cameras is to catch her rages and other behaviors. Seeing what the child does on video often causes the doctor to treat the issue far more seriously than he would just from a parent's verbal description. At least that was my experience with several doctors. The video made the intensity and duration seem far more real. If you cannot put cameras up in your home, try to use your phone or tablet to take video unobtrusively.
What do you do when she screams for hours? What reaction do you give her? Have you ever just pretended she was not there? Left the room to put on earplugs and then taken the time to read a book or have a cup of tea or do something that you enjoy doing WITHOUT her? Do it as long as she screams. If that means dinner does not get made, well, she wore you out with all that screaming, so dinner will have to be cheese sandwiches or something like that. Maybe if you do this for several weeks of her screaming, it will stop. Of course after you ignore her the first time or two she will get louder and go longer to get your attention. Persevere to give zero reaction and it might taper after that. Of course you might have already done this and not had it work.
One thing I found extremely helpful with my own difficult child was the book The Explosive Child by Ross Green. It sounds like this might help you a lot. I also highly recommend Parenting Your Child With Love & Logic by Fay and Cline. This book was very helpful with my son. I know our schools use this too.
Has anyone ever done truly in depth testing on your stepdaughter? More than just an appointment with a psychiatrist or psychologist? I would strongly recommend having her evaluated by a neuropsychologist (psychologist with extra training in the brain). This would entail about 10-12 hours of testing over several sessions. It would be worth bribing your stepdaughter to cooperate in the sessions to get the information. Often they are able to really pinpoint what is going on and direct you to more effective help.
Please don't ever feel that you have to take all of the advice that we give. We offer what we know in the hopes that something that we can share will help you. We know that you cannot do everything. We expect you to take what works and leave the rest. I would urge you and your husband to always, always listen to your instincts, no matter what they say. If they go against some doctor, ignore the doctor. The times I made the biggest mistakes with my kids were the times I ignored my instincts. With a child who was kicked off of probation, you cannot afford to ignore your instincts.