I still don't understand your reasoning about the prenup. If your wife leaves you, even if it were 100% her fault (usually it's not that unilateral), are you not still obliged before God to continue providing for your children? And providing for your wife also indirectly aids your children. So I have no problem with the way the current court system works in making sure that a wife and children are provided for even after a separation. It's actually very well in line with Catholic moral theology. As I've repeatedly said, this idea of it being "unjust" to divide marital assets and make the husband provide for his wife and children comes from this notion that if she leaves due to her own fault that she is no longer entitled to receive support for her children from the husband. That's false. And in such a scenario, why does the husband need to retain all his goods? So he can start a new family? Finally, in the traditional roles, often the wife stays at home to raise the children and therefore does not develop a career that she could fall back on to support herself and her children. Consequently, all the MORE reason that the husband should be legally bound to provide support. This secular thinking regarding prenups is contrary to Catholic thinking in a lot of ways.
Now, the one thing that IS unjust about the divorce laws, is this notion that the wife nearly always retains primary custody of the children. In a Catholic state, if she moved out and shacked up with someone, she should NOT receive custody of the children because of the horrible influence it is for the children to grow up in a household that's sinful in its makeup.