Oh my. What a mess. Okay. If you really want to change this situation, it’s time for you to take a deep, deep breath and a huge step back. Obviously, screaming and crying and going after your boyfriend doesn’t work. He’s now gotten so used to the explosions they have no effect. You have to decide if you want to be angry or you want to be effective. If effective is what you want, I can offer at least a few suggestions.
First: Understand that when you decide to be in a relationship with someone who is almost a generation older, you are deciding to fold into his life and to accept that he is who he is. It is highly unlikely that he will change much for you. He has lived the way he lives for almost 50 years. As much as he cares for you and the children you have had together, he has already shown you that he isn’t motivated to make major changes.
Second: Let go of thinking of the 17-year-old as your babysitter. She’s not. She’s his daughter. She probably has strong feelings about your relationship with her dad. You are closer in age to her than to her dad. She doesn’t see you as a mother figure. She doesn’t see her half-sisters as her responsibility. It is likely that she resents you and the kids for being the family that replaced hers. You’d do much better to try to befriend her than to try to lay down the law. That being said, you and your boyfriend do need to have a calm and thoughtful talk about the living arrangement and what can be reasonably expected of her. My guess is that he isn’t giving her rules because he thinks he is somehow making things up to her for leaving her mother or for not having the kind of family she wishes she has. That ultimately isn’t going to be helpful for her. At 17, she needs his love and support — and she needs to have his counsel in figuring out what she needs to do to become an independent adult. That might be college or a job or a gap year experience. But whatever it is, it doesn’t necessarily involve helping you. Hopefully, if you can bring the emotional temperature down in the house, she will make relationships with her little half-siblings and want to help. But that will come later.
Third: When you yell, he can’t hear you. When you resort to drama like threats to kill yourself, he takes you less and less seriously. The two of you need to learn some ways to communicate effectively. He leaves because he hasn’t a clue how to deal with you when you go off. You go off because he leaves. And around and around it goes. If you two want to save this relationship, you need to get into some couples counseling and learn some communication skills.
Finally: You are absolutely right. Your children shouldn’t be going through all this. Please get connected to a parent education group or family resource center where there are classes in how to manage taking care of young kids and where you can meet other parents in the same stage of life. I’m very concerned about how alone you feel. You need a support system of other young parents so that you have people to turn to besides your boyfriend. You need a network of babysitters to draw on so you aren’t dependent on a reluctant stepdaughter.
I suspect that one of the reasons you aren’t married is that the two of you haven’t been willing to make the commitment when things are so emotionally difficult between you. Do what you can to settle this down so you can focus on making a loving and nurturing family for yourself, your children, and the man you loved enough to decide to bring two children into the world with him. You were right to write. You all deserve so much better than this.
I wish you well.