If a long-term marriage has problems, is that ever an excuse for my spouse to date and have an affair outside our marriage, no matter what our problems are with each other? (United States)
No. God never excuses affairs in any marriage. Jesus taught, “But from the beginning of the creation, God made them male and female…and the two shall become one flesh; so then they are no longer two, but one flesh. Therefore what God has joined [...]