Do I Give Up? Its So Hard To Be A Step Dad!?

My question is. I have a 16 year old stepdaughter, that I have raised since she was four years old. I have brought her up to be a responsible,self efficient and strong young lady. Her biological father lives in Ohio and thank God that he does. Why is it that when men like myself do what is right by his step kids the real dad acts like an ***? If your in a relationship with a mother that has kids then you know, that all men not just me should treat the kids right . This I know. I love my daughter from my heart. But this guy waits ten years later to start talking sh*t to her. She is starting to seem different now, so I asked her what does he say to her on the phone when he calls? She said the he makes statements like, you know I your real daddy. I have this much money or this job title, you know ignorant stuff. The man is always asking about me and her mothers personal business and causes me to take the phone and curse him out in front of her. It's sad though because, All the while I was raising her I always told her that her real dad loves her and she is just bless to have both of our opinions and that we want the best for her. She seems like she is now cought between the two of us and I don't want her going through this now that she is sixteen and dating. Icall it danger days, from going through all the things that teen do these days. I was the one she called from school when she first got her period and man that was when My hair started turning grey. She did not call her mom she called me to come to the school to pick her up. I was a nervous wreck that day. But you see I never tried to take his place I just did what my heart led me to do. Now that I am having some financial problems she has turned to him more these days. I am unsure if I am somewhat angry at her now because she now let this guy stir up things with our family. Because of him buying her love with gifts, and he gives her advice that are causes her to talk back at times. And now I seem to be the mean dad in her eyes because I enforce the rules. Its hard to try and keep her away from her negative, incroud type of freinds that she now deals with. Why? I feel that they, may or may not lead to trouble. Part of me feels cheated. But Im am proud to have had the experience, She will always be my little girl, but sometimes I want to give up on this. What do you think about this?