There is a book I read from time to time called "Don't Let Your Kids Kill You" it's geared towards dealing with kids who abuse alcohol and drugs. But it also is helpful for any situation where you're having difficulty with adult children.

It has good ideas about coping mechanisms. The stress of dealing with an abusive child can literally kill you. At the height of the horrendous relationship with my daughter, my hair was falling out in clumps, my nails broke off at the quick and would bleed. I had high blood pressure, heat palpitations, asthma so severe I could barely breath. I was dying...emotionally and physically.

Since got out of that mess my health has improved significantly.

There may be a way to salvage your relationship with your children. However in the meantime, take very special care of yourself.