Sorry to hear what you are going through.
My partner and I have been together for 13 years...the longest relationship of my life. When we argue, I'm always the one saying "I'm DONE!" She is the persistent one that won't let me go and so far, that makes me the lucky one. Our situation is different than yours, for sure. I have depression, she has O.C.D. and at times, our mental illnesses 'don't play well with each other'.
I've done a lot of 'soul searching' to try and find out 'why' I say 'I'm done!' and what I have discovered about myself is that it seems to be the only 'thing' I can change...it's the only thing I have 'power' over. The saying "The grass is always greener on the other side of the fence." doesn't always mean wanting another person. It means, to me, a feeling of powerlessness over situations and conditions. So, the one thing I can 'change' is who I share my life with. It's not fair to her, obviously. It's a pattern in my life. One that I desperately want to change.
Why your wife feels this way, I have no idea, only she knows.
As for the outcome of your situation...why do you assume she will get custody of the children? Are you not planning on seeking custody of them? Times are changing and fathers can do single parenting just as much as mothers. Why do you say 'she understands she will have to sell the house'? Is the house only in her name? You say 'I am going to have to suffer the outcome of losing my house'. You say you 'did things around the house for her, took care of the kids...' like you were doing her a favor. Those responsibilities are part of the package, not something that earns a partner and parent a pat on the back. You say "we have had friends and family 'jealous' as to how good I treated her", as if that isn't to be expected. How did they know about how good you treated her? From you or from her? Were you boasting or was she?
No one gets divorced for no good reason. Just who is this person that told you 'perhaps she is going through a depression and mid life crisis'? Who are you talking to about your issues? Why do they assume it's 'her' problem?
I'm sorry if I sound harsh. Looking at our own part in things is not always easy. Examining our motives for everything we do can be painful but enlightening.
My Aunt and Uncle got divorced, then after several years apart, they moved back in together without remarrying. One never knows what the future holds.
Get some counselling for yourself so that 'someone' won't have to wonder if you are 'going through depression and/or a mid life crisis'.
multiple surgeries for rotator cuff both shoulders with residual chronic impingement syndrome, ulnar nerve transposition, carpal tunnel release, wrist ganglionectomies/denervectomies/tenolysis, multiple herniated discs, tarlov cyst, whiplash, bursitis of hips, tendonitis, torus, 3rd degree shoulder separation, torn labrum, ovarian cysts, fibroid tumors of the uterus