Boyfriend not allowed to be a father?

My boyfriend has a 7 year old daughter who the ex-wife forces to have supervised visitation (she has no proof as of why besides stating he has a small temper). During this his mother was deemed the custody supervisor. Problem is she is trying to push him out of the picture. He is not allowed to say or do anything that contradicts her “up bringing” of this child. Ive given him what advice i could but because im not directly involved there is only so much i can do. Already knowing she is possibly not his he is getting a DNA test to clarify that first… But if she is his what should be the next step? Hes been fighting to be a father but everything he does she unravels. Hes beginning to give up…