Jane, I'm sorry that you can't count on your mother for kind words instead of criticism. That's not fair. I agree maybe some distance from your mother for a while might help.
You are doing well. Fits and starts is how I quit. You have great insight. If you ever feel trapped and angry and frustrated by a discussion with your mom, or anyone, try counting to ten, take a deep breath and say the serenity prayer. Even if you aren't religious, just send a plea up to the sky to grant you the serenity to accept the things you cannot change, courage to change the things you can and the wisdom to know the difference. That's saved my butt a bunch of times.
Hugs!