Hi Coly, I think OwnIt is right on the money with her advice to you. There is a repeating cycle in your situation, and it is good to recognise that and change it up if it isn't working for you.
I could list many reasons I have read on this forum for a mid life spouse leaving a marriage. They range from - you bought the wrong flavour of crisps to you didn't dress provocatively enough...etc.
But the real reason is the MLCer came to feel hollow, empty within themselves and believed you must be the cause. Of course you aren't....it is more about their coping skills and believing that another person will 'make' them happy.
It strikes me that you may be in the bargaining stage of grief - if only I could....then he would...and we could...
But actually, there may be nothing you can do for your situation with him right now - other than let him follow the path he seems to need to follow..
Xx
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus