I say do not cut off contact. However do take control of the contact. Most of it appears to be by phone, which is great for this technique. When the parent starts acting emotionally abusive, simply tell them so in a calm voice, and explain that you will hang up if it continues. No goodbyes, no second chances, just hang up. You can try again tomorrow. At first the abusive parent will deny they are being abusive. They often really don’t know, but have just lived life in reaction to their own subconscious angst. Only when their abusiveness is truncated by you, and the reason given will they begin to do the thinking that will lead them to self realization, or at least positively changed behavior. I know of one abusive parent that never did realize his abusiveness, but he did change his behavior on the basis of “My kids must be oversensitive, so I will be more careful around them.” lol That’s better than nothing.