You cannot deny the conflict in both your positions that breeds the resentments on both sides.
I think you need a prenuptial agreement that covers both of your concerns. Just the act of negotiating one will bring to light the fears and attitudes behind the feelings that make this a conflict between you in the first place.
I feel you have been asking the wrong questions, and have not dug deep enough into the feelings behind the attitude. He has been telling you all along what the married status means to him, and wanting another child, adds to that attitude. He simply doesn't want the added responsibilities, financial, or otherwise, that marriage brings to his life. That's where your talking should be going, to the benefit of being married in a practical sense, to off set his fears of the added responsibilities.
Bottom line is you have not truly explored his deep rooted attitude that makes this a conflict in he first place. Until you both can and do, your desire to be married will be met with his desire NOT to be. So far your entire case is based on what you want, and his on what he wants.
So let me ask you in your own words, how does being married benefit HIM?
I have been married 37 years and I know the benefits that I enjoy, clearly he does NOT.