Should and how do I leave? Please help!?

I am 17 and live with my mom and step-dad. My step-dad is bipolar and VERY controlling. I have had a steady, part-time job for over a year. I am in NHS, band, FFA, and make very good grades. Every time I am home I am, constantly in trouble because I "didn't do the dishes" or that I "am never home and need to take care of my home responsibilities" even though my step-dad is the one who forced me to get a job in the first place. My step-dad often yells and honestly does things just to be mean, he says that's how he was raised and so that's how he treats us. I am not lazy and am a very kind person, I am just fed up with being treated like a dog. My step-dad has a 23 year old son, however he never knew he existed until he was 12. This is when his son came to live with him. He left his own father's home at 15, only 3 years after first meeting him, because of the way my step-dad treated him. I have everything planned out as to rent, bills, school, and my future. I would be moving in with my boyfriend who also has a steady job and is currently enrolled in college. We have been dating for over a year and me leaving home is not because I'm "in love" or "want to always be by his side". I would be living with him because his parents have a house that they let him live in and we wouldn't have to pay rent, just bills. We also work at the same place and it would be convenient. However I am not unrealistic about it. I know it will be hard but I've had time to figure stuff out and my family says they completely understand, they do not like my step-dad either, and will support and help me. I am tired of being treated this way and just need some advice, I only have 1 more year of high school and would be attending the same school I always have and would continue to work as I have since sophomore year. I will turn 18 this December. Please help!