It is very hard to argue and change your mother's point of view if you still live under her care and there is no prospect of you moving out soon. that's just how it is. They are so conditioned to be overcontrolling that they don't know how else to act. Old habits are hard to break unless they gain some new perspective. Therefore, if they realize that you are going to leave the house soon and move out, they may start using every trick in the book to please you and conform to your wishes in order to keep you in their house forever.
I think what will really help things is moving out. I have overprotective parents, and when I brought up the suggestion of moving to a new place, my mom cried and begged me not to move out because she was so dependent on me. Its oftentimes the controlling overbearing parents who have a harder time coping with the idea of their child fleeing the nest.
I would have left the house a long time ago if it wasn't for my social anxiety. I used to quit part time jobs due to the social anxiety I got during work. Now my only excuse is to get a loan and move away to school. If I were you, I would try to move out before your brother did as well, because then the absence won't be so hard on your mother, she still has one child left at home for her to control.
Hell, you know what? I was registered to move away to school this coming May for a nursing program in a college 3 hours from home. I had my parents sign forms and provide me with money for the registration process, but as it turns out, the May session of the program is cancelled until September. As soon as my parents realized that I was leaving soon, they began to treat me a lot better than they did before. They wanted to gain my respect since I was expected to leave the house soon. They stopped bothering me and criticizing me, and let me do whatever I wanted.
Therefore, I believe that either threatening to move out or actually moving out can seriously change the dynamics between you and your mother. All you need is the financial freedom to do it, because once you're out of there, and have enough money and resources to sustain yourself, it is easy to cut off ties with your mother.