Complicated relationship question?

I've been with my fiance for 4 years and we have a 9 month old baby together. Our child was unplanned but it happened and now for lack of finacial stability we live in a back house on his parents property. I get along with his family ok but not great. His family can be very two faced and his dad disrespects me all the time and he thinks its funny. My fiance rarely defendsme. We fight a lot about his family but we can't move because of the fact we have no money to. I'm going to school and he's working full time. He often leaves our house randomly and won't come back for hours sometimes ( he goes to his familys house without letting me know where he is going or how long he will be). He is catholic(doesn't practice it) and I'm christian. He won't meet me in the middle abouttha though.his family has even told him in front of me that if he goes to church with me they will brainwash him. Anyways I do know that we should've thought about this before having an unplanned cchild but what done is done. I just feel like I had to grow up fast(I'm 21) and he keeps making excuses for why he can't stand up to his family and why he doesn't help me with the house and our son(he's 23). I'm fed up. How can I get it thru his head that he needs to grow up? I won't marrry him until he gives me some sort of sign he will man up. I've told him many times about this but he always defends his family and when I say I will get a job to make more money he says he will leave( his pride). I've thought about leaving but I have no family to help me and I still love him. What can I do?