Roxanne, I'm glad to hear that hemp seed oil has been doing wonders for your child.
However, you might want to also look into medical cannabis... Here are some excerpts from mothers with autistic children and how adding cannabis to the child's regimen has greatly improved the child's behaviour
(Source: Autism.org)
"My son (who is almost nine years of age) has been on medications to address his severe autistic behaviors including aggression and throwing fits over trivial issues in the environment. He has been difficult to instruct due to these behaviors. None of the medications has ever made a difference, except for making his behaviors worse. He has been through the whole range starting at three and a half with ritalin and dexedrine, and going through prozac, paxil, clonidine, naltrexone, adderall and risperdal. Finally, we gave up on medications and decided to manage his behaviors through behavioral techniques. We had mixed results.
A few months ago we tried the prescription drug Marinol and noticed a drop in the severe episodes, no fits and little to no aggression towards his teacher and family members on a daily basis. A few weeks ago we started him on cannabis and stopped the Marinol. He has been in a much better mood and is much easier to keep on task in the classroom now. There has not been a major fit since he started the Marinol, and the cannabis seems to work just as well with his behaviors and he is now much more easier for his therapists to manage during instruction.
It is not a cure, but just a tool to make things go smoother and prevent disruptions in his learning. He still has days when he gets angry and moody, but we can adjust the dose to help him through those days. It is such a mild medication and there are no long term side effects that can damage the body's organs. I feel much more comfortable administering cannabis) than something like risperdal.
Autism is an unpredictable disorder and even though major behaviors are constants, autistic people have different degrees of their behaviors from day to day. We can tell when he might need an extra dose to get him through a rough day, and due to the fact that there is no toxic overdose, we do not have to be overly concerned with safety issues."
--From a less stressed out mom
"I know it's not the end all answer but it's been the best answer for the longest time for us in regards to ALL the other medications. I cannot tell you how many months we would go on a medication wondering if it was doing anything, anything at all. Here we can see the difference in 30-60 minutes guaranteed."
Since the hemp seed oil (which is obviously derived from the cannabis plant) has shown a marked improvement for your child, then I strongly believe that adding a small amount of cannabis will also benefit your child.
However, if you think you have his behaviour under optimal control, you should probably stick to the regimen that you have now... and if you do decide to try administering cannabis to his regimen, start the dosage very low.
As for dosage, I would suggest to start off with 1/16th of a gram of cannabis prepared in a "Leary Biscuit" (1/16th of a gram is a very low dose and should show you its minimal effects).
If you notice an improvement after a couple of weeks, then you could increase the dosage to 1/8 of a gram and keep him on that regimen for at least a month before increasing the dosage again. If you still see marked improvement after increasing the dosage, then I would say it would be fine to adjust the dose every month until you find the perfect dose.
Step 1: Take a cracker

Step 2: Take a small lump of butter or cheese (Cheddar, American, etc.)

Step 3: Place the marijuana on top of the cracker

Step 4: Heat the cracker in the microwave until the cheese has melted
I recommend to split the cheese in half and put the cannabis in between the two layers (rather than placing it on top of the cheese, which will expose the medicine to the microwaves).
That way your child will get an optimal effect from the medicine.
Also, make sure you are using the lowest setting on the microwave (you don't want to overcook it).
If you need further assistance, please feel free to send me a private message and I will get to your message ASAP.