I am so sorry for your situation. It is very disheartening to try to convince someone that they are acting foolish. He seems to have created a scenario in his mind that has turned this infatuation into love. Unfortunately we can't convince anyone of something they refuse to see. I would love to say that he will see the light but he has to create his own choices. In time he probably will see the light because lies always become obvious in the end. No situation is worth killing yourself over. You have two children that depend on you for a positive example. You have to be okay for them. Children learn valuable lessons from negative choices.
You can approach your husband about mending your relationship through therapy but he has to want to go. The better choice is to enroll in getting help while you are withstanding such horrible treatment. He may realize that he is crushing your heart. In the end he has to make some choices that do not destroy his family. Have faith that you are keeping your family in your sight at all times. He may realize that someone like her is not love but just a selfish distraction.
If you do not offer positive feedback I will not be compensated