For the record, and to add to my last post, my abusive ex husband also had untreated ADHD, but it doesn't matter what your fiance's diagnosis is. It really doesn't. What matters is how he treats you and how you feel being around him. It's still abuse, no matter how you slice it, and no matter what his diagnosis is. You do not have to sit around and wait for him to initiate and obtain treatment for his ADHD in order to improve his treatment of you. Even if his ADHD is influencing some of his angry reactions, the constant berating is likely not even linked to his ADHD.

Do you really want to be dealing with this, is the question? You're in for one hell of a ride with someone who is not treating you right.