The behaviors you describe are abusive. And he certainly doesn't have POA over you.
It may be time that you start meeting your own needs, that you insist on driving yourself, alone to therapy, and that you actually allow him to solve his own problems. If you are actually taking care of his mom at all, tell him you want to be named as secondary POA. Otherwise, leave it to him to arrange for whatever assistance she needs. Seriously. You are describing an unhealthy relationship and, as said before, I certainly hope you are talking to your therapist about this.