Just read through your sitch. Sorry to hear it, but it's pretty typical for a WW in the thick of an A. My story is very similar to yours, but I have 4 kids, all boys, and much younger than yours. My WW left a stable relationship of 24 years to live with a guy she had known maybe 3 months. I really feel for you, and it's especially difficult because you've been through this before. At some point, you ask yourself, will I ever be enough? Based on history, it seems your W is unhappy with herself and is blame shifting onto you.
As much as it hurts, maybe a separation or even D is the best bet for now. Give her time away to go through that journey. I hate to even suggest it, since I don't believe in D, but you can't make someone want to be in a M. My gut feeling is that your W is never going to appreciate what she had with you, until it's gone. You have to decide for yourself how much you can take and how long you are willing to wait to see if she ever comes around. Definitely focus on detachment and GAL for now, as it's likely to be a very long road home, even if WW does change her mind.
I really don't get what happens to women in mid-life but since DDay, I have talked to dozens of men who have gone through very similar situations. Seems like women hit 10-15 years of M, have a couple of kids, and then start thinking they missed out on something in life, and blame the H for all of it. I know that there are men who go nutty too, but seems like I hear about the other way around more often. And I don't really believe they ever end up more "happy" years down the road than what they could have been had they put in the work on their current relationship. But as the LBS, not sure what choice we have but to work on ourselves, and keep moving ahead with life. Good luck brother, I'll be thinking of you.
This post really hit the mark with me. I feel blessed and lucky that my WW getting busted and me demanding a D snapped her out of her funk and we were able to piece back together our shattered home. Some don't snap out of it. Some snap out of it but are too ashamed of themselves to reach back out to those they've hurt.