I am sorry to hear this sad story. Your mom and you are not lucky to meet this kind of guy. I can understand that how stressful you and your mom are. As you are not independent, things are quite difficult right now. However, things may not that bad. I have two suggestions for you.
First, ask that man for sponsoring green card for your mom and you as soon as possible, since you have been in US for almost one year. I don't know the procedure, but it is relatively simple, easy and fast. As this guy is married to your mom, he must bear this obligation. You can ask someone at church for help. It would be better if someone who know immigration law can help you. It seems to me that your stepfather may not be willing to attain a lawyer to handle the cases.
Second, I don't know how old you are. I hope you study hard, and go to college early. If you can stand by your self,your mom's sacrifice would not be in vain. May God bless you and your mom.