B..
SO...what are you going to do when he meets a woman he DOES want to commit to? Do you really think that woman will want you around "co-parenting" when that should be her job? Do you really think she will want his friends with benefits raising who is HER step daughter? Do you think she will want you to live there? Do you really think she is going to arrange her life, so you can have your time with her? Do you really think she will want her calling YOU mommy, when she will be the one doing the raising, and financially caring for her?
I'm only trying to be helpful. What you are doing is harmful for this child. You are NOT her mommy. You will NOT be around forever. You are NOT a family. You are presenting this child with a picture, that is not the truth. You are setting her up to be incredibly hurt. You have no legal, emotional, relational right to this child. When someone else comes along, you will be the burden. The child will be the one hurt. The right thing to do, would to STOP presenting this child with a family picture. You are not a family. You are not her mother. You are there, for now. Until something else happens, until someone else comes along. Until he no longer needs you. You ARE being used by him. He is manipulating you, by your affections for her. He knows you will be around for sex and to help him, because you care for her.
This situation is temporary. It's dysfunctional. It's unhealthy. It's a lie. You WILL hurt her more then she is being hurt. You are fooling yourself, if you t think you are any more to him, then a convenient sex buddy, and help for his daughter. You are NOT a permanent fixture. You are hurting this child, can you really not see that?
You are not her mommy, and never will be. She is not your daughter and never will be. You are not in a real relationship with him, and never will be. You are not a family, and never will be. You are playing house, at the expense of a child.