golf mom, You've come a long way in your life, you are a successful woman who is going to survive this situation. Healing will take time because you have put all of you love, trust and faith in a man who had a lot of issues before meeting up and marrying you. I suspect his issues were carried over into your marriage and now, after a long time, have come to the surface again. He didn't make the life transitions correctly in his teens, 20's and 30's.
In your posting, you described what his life was like before he met you....well he and his history have now come full circle and he's going to have to face those issues head on or remain on the run going from one relationship to the next. In many ways, his life sounds like my xh's...
Please do not second guess yourself. You fell in love w/this man and had a good marriage until mid-life hit and another life's transition came upon him. I think you are too hard on yourself at times and you need to remember that this mlc is his journey to take so that he can face his issues and become a mature man.
Please be kind to yourself...you have done absolutely nothing wrong...
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.