I know this is fairly quick to have a follow up post but I'm excited and wanted to share the news. After reading all of your responses I talked to Fi and convinced him that now vs. later was the best time to have the talk with his ex. He met me with some resistance (there's background story as to why but that's a post for another day) anyway...finally he agreed to do it at tonight's drop off. Well she took the news well and congratulated him and asked him to send me congrats from her. I'm glad he did it and I feel better now that she knows.
Thanks again for all your words of wisdom!!