Oh my god...if everything just "worked out" would ANYONE be on assistance, struggling every week, poor, not able to adequately support their family, etc? OF COURSE, it doesn't just "work out." I'm sorry if that seems harsh, I'm really not trying to be. You are coming from an emotional point, and he is coming from a logical one. It's a common occurrence in marriages with many things. Few things carry the weight of another child, though.
If both don't desire a child, you don't have a child. It's that simple, and that difficult of a pill to swallow. Who provides for the children? Who carries the stress of being the bread winner? Who is responsible for paying for food, clothing, transportation, activities, health care, college education, things for you, things for him? Who actually HAS to bring in the most money, to raise this family. Who is the most relied on? Since he has two jobs, I will assume it's him. (Correct me, if I'm wrong!) If he feels he can't provide, what is he supposed to do? Work three jobs? Quit and get a really good paying job, that could in on possibility never come? You are bringing it up, you are making him angry. Are you listening? Are you respecting how incredibly hard on him 3 children would be? Men are different. So much of their self worth and purpose is tied into how well they can provide. He doesn't think he can. Listen to him, and respect that. You can not and should not try to force a child on someone. Not only is it wrong, it breeds deep resentment. I have seen it end marriages, or simply result in terrible ones. Here are the facts. You do not HAVE to have another child to survive. He HAS to provide for your family, for it to survive. If he is dead set against it, it should not happen.
Do not continue to pressure him. He is angry, and he will continue to get angry. His requirement as your husband, is not to give you a child when you want it. It's to provide for your family in many different ways, including financially. If you don't mutually desire another child, it can't be forced.
P.S.
Yes, things have work out for many since the beginning of time. It also hasn't worked for many. In our world, our economy, the financial climate...it's getting harder and harder for things to just work out. Sometimes, down right impossible. I don't think the fact that things just end up working out for some, should allow anyone to overlook, not plan, and not think about what would happen if it doesn't.