Hi again and thank for the additional information,
From what you describe, it is possible that son has Sensory Integration Disorder (Sensory Processing Disorder) and his behavior is a response to the uncomfortable symptoms this causes. This disorder involves an area of the brain that regulates how the sensory stimuli from the environment is received by a person. So they might be oversensitive to light, sound, touch (the way clothes feel on skin), taste, smell and movement. His aggressive and oppositional reaction is common in children with SPD. It is their expression of the discomfort because they can't help it, they don't understand it and they do not have the words to describe it.
The assessment of treatment of this disorder is by a pediatric occupational therapist who specializes in SPD treatment call sensory integration therapy. Once the physical discomforts are addressed the behavior improves.
Now, this is all complicated by being a child who has been abandoned by his mother. The feelings about this can also be expressed in aggressive and oppositional behaviors. Then, individual psychotherapy may be helpful. But if the SPD symptoms are there...I would start with this and consider psychotherapy if SI therapy is not effective. None of the behavior management strategies will work until the underlying cause of the behavior is determined. (Also, he is able to control these behaviors at school...that is good...but it all overflows at home because it takes energy to hold it in and he becomes fatigued...in addition, home is a safer place to express his emotions)
If you would let me know if you think SPD is a possibility and provide me with your location, I can search for some resources for you.
Here is on line information about SPD:http://www.spdfoundation.net/
I hope this is helpful. If not please let me know and we will continue our discussion.