Hi and welcome....I have seen absence seizures that do involve a head nod type thing. Not sure if that is what your son is doing now. Has the doctor tried an eeg around that time when he has them>? That would be the best way to tell....
How long are these lasting? I know you said they last until diastat. I would see if you can arrange to take him in to see a doctor during them if possible? Might not if you are too far away. Just a thought.
Cleveland clinic is good. I also hear great things about rainbow babies, I think it is called in that area as well. You may have a long wait to get into cleveland. Many find it a great place....
Best wishes for help!