Personality Disorders Support Group
Personality disorders form a class of mental disorders that are characterized by long-lasting rigid patterns of thought and behaviour. Personality disorders are seen by the American Psychiatric Association as an enduring pattern of inner experience and behavior that deviates markedly from the expectations of the culture of the individual who exhibits it.
I'm so sorry you're going through this. From what you are saying, it appears your son relies heavily on you, and has almost always done so for his entire life.
You may want to ask yourself, 'What would happen if I did walk away?' When your son tells you that you haven't been helpful to him, that would be a great segway into telling him that you were thinking it might be best to stop doing so. I think you name it correctly as emotional abuse, since staying and helping is not to his satisfaction and he gets to berate you when you do help.
This is not healthy for you. if you want to walk away, do so, and without guilt. While I don't know all the particulars, he is 50, meaning he needs to handle his own affairs, and likely can. Having a personality disorder does not mean someone is not functional.
You may want to view it this way, if it helps: you staying to help could actually be hurting your son by delaying his needed action on his own life. If he thinks you as his mother should 'fix' his life, he would have no motivation to do so himself, keeping you both trapped and miserable. Seeing a counselor on your own would be beneficial, to help sort out your feelings and support you in whatever move you think you need to make.
It can be so difficult to stop helping a family member in particular, but often it ends up being best for all involved. Have you spoken to your son about your feelings? He may share them, and want to handle things on his own anyway..
For calming, there is a great variety of tools that are helpful. You may want to look up 'box breathing' and other calming tools online. They really work!
Peace to you, and share more when you can. Writing it out often helps more than we think.