Broken

My Husband of 16 years has been diagnosed with ADHD.  He has 4 stages according to the Amen Clinics.   We are in active counseling and working to supplement his diet to manage the ADHD.  He has not yet taken the steps towards medication which is a huge problem for me. 

It seems like everything begins to go well and then "bam" the wrecking ball flies and everything comes crashing down.  I have two children and went through many confusing years of what was wrong with me.  My H has a horrible temper and has been verbally abusive 98% of our marriage.  Adding kids was a huge heart break and dream killer as what he said he wanted has only seemed to prove to be a stressor for him.  I have grown stronger over the years and probably break all the rules when it comes to protecting my children.  But yesterday was a whole new low for us.  For whatever reason H was agitated and already beginning the signs of confrontation when we decided to head out of town for a family members bday.  By the time we hit 55 miles out of town, we were in a full fledge argument.  I decided I didn't want to see family and pretend like we were all good when signs of stress were all over my face.  I took the next exit and headed back home.  This was a huge mistake as my H went into a ADHD rage.  I was unable to talk him off the cliff and after several spouts of profanity and blaming... he demanded to be let out of the car.  We were at a point on the freeway that was beginning to descend a curvy hill 75 mph.  I told him No, I won't leave you on the freeway.  He continued his ranting and demanding I stop the car.  I again said no.  He then threatened to throw the car in reverse if I didn't stop the car.  I couldn't believe it.  My son began to plead with him.  I told him to please let me get down the hill and I would stop.. He put his hand on the gear stick and demanded I stop now.  Of course, I did.  I had to take a moment to calm my self but my son down as well. 

I am concerned as anger seems to be a common issue in ADHD but is this kind of anger/rage normal?  Yes, he needs medication but will this really help or is it time to stop this madness and protect myself and the kids?  I love my H and I don't want to give up on him but I am at a complete loss of what to do next?