Boyfriends overbearing mother.

Hi,
To first start off, my boyfriend,20, and I,19, have been together for almost two years now. When we were almost about a year into our relationship, he was talking about marriage, and moving out. I was excited for it, we opened a savings account and had $900 saved up to start our new life together (which we were going to keep saving) well his mom asked him why all the money is saved up and he told her we were thinking about moving out or going on a big vacation(which was not the truth) and she did not like that, sat us down and told us that if we moved out that she would not let him see his brothers, or would not support our decision. So I got fed up with him listening to his mom and just said fine, we are not moving out. So when we spent the money his mom felt secure that we were not leaving. About the marriage part, his mom told him that he cannot move out or get married until he is 26 years old. And with him telling me that we will soon and that he was excited and everything, I got really upset and emotional. Well needless to say we are not doing either of them and every time i bring one of those subjects up, it seems to upset him. I just feel that his mom is way to over bearing and I just need to know how to handle it. His mom always needs to know where he is, always checks up on him, and always calls my phone when he does not answer his phone. She always makes him babysit his brothers, 16, 13, and 6. Why would he if there is a 16 year old capable of doing it? I mean, she acts like he is her husband, even though she has a husband that lives with her and they are perfectly fine, but when her husband is at work, she wants her son to be there for her and babysit, clean, cook and make sure the kids get showered and are in bed at 8 sharp. It makes him seem to play the role as husband and father. I just cannot stand it and I need advice on how to deal with it, because I feel like this is straining our relationship and I just do not know what to do. What would you recommend me doing? Thank you for the help!