If you are in Texas, THC is not legal. Some have been having luck with CBD oil, but I don't read many posts saying it helps for severe aggression. And, it's pretty hit or miss because the CBD oil companies don't say the strains of the plant their product is made from, in most cases.
You may want to consider hooking up with Mark and Christie Zartler who are trying to pave the way for the use of medical marijuana for autism in Texas. They are using it with their daughter successfully (after many legal battles, including CPS, but they had tried everything else).

Hi. Did you decide to try it? I am presently adding it to my son’s medicine. He is 15 and can get violent when he has meltdowns. Hoping I have someone to compare notes to!