Infidelity Support Group
Any relationship in which one partner engages willfully in sexual relations with another outside of the partnership is considered to have experienced infidelity. This breach of trust is often traumatizing for the faithful partner as well as the relationship, and support is often needed to heal emotionally and to decide whether or not the relationship should continue after...
I am not in your exact situation, but I had an affair with someone who meets the criteria of a sociopath, and it has been a nightmare to get him out of my/our life. His wife also did some stalking and harassment early on, but I tend to think her actions came from a combination of understandable anger and mental issues stemming from being married to a sociopath for many years.
Also, the sociopath affair partner often uses the affair as a game or manipulation to poach someone from their marriage, hence the rage if they don't "win."