I think this is pretty on track. You might want to consult with an attorney (maybe you did) before throwing down the child custody gauntlet.
I would not concern myself with OM. He is just being male. He may not even know who you are and if he does god knows what lies she has told him about you to justify her own behavior. You will get no lasting satisfaction from this. It will driver her further toward him, and she is likely to replace him if he drops her.
Me: 39 W: 38 T-18yrs M-13yrs 2 Girls: 10 & 3 EA BD 5/24/15 Separate Bedrooms 6/12/15 PA BD 7/3/15 Separate Residence 8/8/15