So, your actual problem is the legal expense and legal hassles involved in divorce?
Many/most of these are to do with the painful untangling of shared resources and responsibilities that come from sharing a life and resources. Marriage simplifies many things for two people - ‘we own this thing together’ becomes much simpler with marriage. The legal process of negotiating whether 20 or 40 or 50% of the house belongs to partner A is what tends to cause the pain.