Fed up

I know this is going to sound like I'm a terrible person but, if you all only knew...My marriage has been ruined by my stepson. My husband is also to blame because he does not discipline him for anything but this kid just keeps pushing and pushing and I'm done. From day 1 this kid (now 15) has been nothing but disrespectful to me. For 8 years I have put up with sooooo much with this kid. He's told his family lies about me from day one, doesn't listen and acts as if I'm the child and he's the adult. He tells his dad to tell me I need to hurry up in the bathroom in the mornings or get up earlier, when I leave a whole hour and a half before school even starts. If I take things for punishment he tells hos dad the next day to give said things back and dad listens. He trys to get my kids (9 and 5) to ignore me and listen to him as if I don't exist. I will be talking to one and he'll stand there trying to interrupt to get them to not listen to me. I could probably write a book if I were to unleash everything I've been putting up with and hopping it would get better. At this point after all these years I'm just fed up. It is not getting better, only worse. My husband does nothing to correct his behavior and thinks he does nothing wrong. I am litteraly about to end my marriage because of a child.