I would talk with a social worker re your Dad's behavior. I know how hard it is to live with a verbally abusive parent and I am glad you are trying to take care of yourself. However the phone calls and threats to call you at work are not appropirate and I can see how this is hard to deal with.
Can you put his emails into spam so you don't have to read them which is causing your anxiety. I would suspect his Therapist does not know of his behavior.
I am sorry you are going through this and I wish I had a better answer for you.