Yes definitely a MLC. Fear of death and dying triggers an intense fear that they have "missed out" on something.
And to be fair, while I never understood MLC, I have come around to seeing why it is more common in some people. I have a family history of longevity and so have somewhat taken it for granted that I too will probably live to 90 or better. Therefore, turning 50 or 60 didn't really trigger fear in me. But for a man, especially if he has known other men who dropped dead of heart attacks in their 50's or 60's, the future might not look so certain. Even I, now, at 64 am starting to think about my bucket list and how I want to spend the next 20-30 years of my life. I'm not having a MLC but I can understand a little better where it comes from. My ex ALWAYS had a fear of death and aging, despite longevity in his family too, and I think it was tied in part to a good friend of his dying of a lightning strike at age 12.
That being said - don't put your daughter in the middle. no matter what. Don't ask her anything about her father unless she volunteers. Focus on showing her that YOU are strong and model for her what it looks like to recover from betrayal and go forward with your life. My kids were amazed that their mom took up playing the drums and then played in a punk cover band and now tours occasionally with a professional musician friend playing percussion. Their relief that I am doing okay makes them feel a little safer in the world that their father blew up.
Find some fun things to do with her while she's living with you. This may be a blessing that can take some of your focus off of your H and provide you with companionship at a time that it is hard to come by. Treat it as a unique opportunity to grow your relationship with her.
Also, be aware she may blow up at you - don't take it personally. They usually vent at the "safe" parent. She might even blame you for the breakup - don't bite. She can't vent at her father without risking losing his love. She's more secure in yours.
Stick to the high road and don't badmouth your H. It's ok to stick to the facts - that he had a previous affair, that you were hoping for marriage counseling/reconciliation but he is not open to that. Divorce is not your choice but you do not have the power to control his actions. That's enough information.
Trust me she will NOT be amused that he is dating women her age.
Maybe you and she can make vision boards together? Might be a fun evening.
Do your crying and moping in private. Her world is already shaken, she doesn't need to be worrying about you too - it only makes her feel more insecure in the world.
