You really have been through a great deal in your young life. You had to grow up very quickly, while your father has stayed "stuck" in his drug addiction and denial. You have been there for your brother, and you do not want to see him get hurt. What does your step-mother do to your brother that is abusive? Has she ever abused you?
You mentioned that your father blames you for his drug abuse. Please know that you are NOT the reason for his addiction. He has made a choice to not get help for himself, and not take responsibility for his actions, and this looks and feels like emotional abuse.
Is there anyone whom you can talk to about what is going on in your home such as a school counselor, teacher or pastor? Do you have another adult family member such as an aunt, uncle or grandparent who can be your advocate and possibly allow you and your brother to live with them at least temporarily? You mentioned that if you told your step-mother about your father's drug abuse, that she would kick you and your brother out of the house? Why do you think she would do this, has she threatened to kick you out in the past?
You said that you feel lost and are not sure how to keep yourself sane. Are you seeing a therapist or do you take medications for your depression? Do you ever have suicidal thoughts or thoughts of harming yourself? Have you ever tried journaling your feelings help you get through when things get tough? Or try creative activities or physical activities to help you cope? When you have a chance, check out some of the coping skills on our website and read what other kids say on: