Hi there JenSMP,
You are really committted to getting what is right for your child and I honor your dedication to your family! I love the Montessori education model, best wishes with that. I am not a medical professional and won't comment on meds. One thing that we have found tremendous success with is the Nurtured Heart Approach to engaging with our child. This after nothing else was helping; NHA changes everything. You can get more info. at www.difficultchild.com or www.nurturinggreatness.net.
I posted about it before in a different forum too.
Best.