Just so you know, BB is a corporate attorney who deals with these issues every day. She KNOWS what works so I appreciate that you followed her template.
Gotta figure out what to say to OM
"What are your intentions with my wife?" See what he says Then tell him that you and your wife are very much still married and that you will fight for your marriage. You will also be taking legal action against him in an alienation of affection lawsuit, so he had better lawyer up, BUCKO. Tell him that there is no future with your wife because he will be ETERNALLY HATED BY HER CHILDREN FOR DESTROYING THEIR FAMILY. His name is MUD in the in-law pool and he will never be accepted there.
Do not pistol whip him!
What about clueless GF/possible exGF?
Give her all the information you have about the affair to prove to her it is ongoing. Tell her that your wife openly admits and talks of her affair at home. Tell her she is being conned.
Ok, can we tighten up this family letter so readers are not distracted by your emotions? You are a good writer, but too fancy for folks like me. In sales we learn that if you don't catch your audiences attention in the first couple of sentences, you are likely to lose them.:
Dear Family,
I am writing you to ask for your support in saving my marriage. Our marriage and my daughters family is being threatened by Jennefer's adulterous affair with ScumBag Jones, her 21 year old co-worker. This affair has been ongoing for a year now with no end in sight. I have done every thing in my power to get her to end her affair to no avail.
While I do take responsibility for many of the issues in our marriage, our marriage cannot be repaired as long as there is a third person in the marriage. Not only does this affair threaten our marriage, but it is teaching our daughters that wrong is right, that adultery is an acceptable lifestyle choice. They are being taught that any behavior, no matter how bad, is acceptable as long as it makes one "happy."
I've come here today to ask for your support of my marriage, and my family, and to ask you to exert whatever influence you can to get Jennefer to end her affair and join me in marriage counseling, and work on repairing our marriage. I am asking for your advice in saving my marriage and DD's family.
Please know that I love Jennefer very much and I'm willing to do whatever it takes to fix our marriage. It's not my intent to shame or embarrass her, but to gain the help of our family.
-Carp