Also now that I'm living by myself (with kids 50/50 but hopefully they would be at least 60% with me eventually it's just a long story) I am looking back in bewilderment that I was "fighting for the marriage" for nearly two decades, while so desperately unhappy so much of the time. Literally WHY the sacred cow of marriage trumps the life of one or two individuals? Marriage as a notion or an institution is not more valuable than an individual human life, which I was totally sacrificing, living this tiny suffocating life to keep the marriage.
As for the kids who also of course were major consideration, there is a lot of research nowadays pointing towards the kids suffering more if they have to witness or share the atmosphere of the household with parents depressed and trapped in their marriages, however the adults try to conceal it and present a happy or neutral facade. For your children it's not a good model of a family or life lived true to your heart by any means. But obviously it's all even worse if children have to witness any kind of abuse.
The kids might still express their wishes like I wish you were still together once you split up, but far more often if they say so it's because again they are still either broadcasting the feelings of one of the parents or the parent who initiated the break up still feels guilt and shame or that they somehow failed or didn't live up to their role as a parent by not also staying a husband or wife, so the child would still express regrets following their cues, not their own.
What each child wants the most is for the parents to be happy, and what is also the most beneficial for any child is to grow up with happy parents. Also miserably staying together puts a burden of this debt for the child when they grow up and realise one or both of their parents literally sacrificed their life for them, which places this implicit expectation that at some point said child would need to sacrifice their own life choices for Mum and/or Dad, and do we want it for our kids?
Anyway, my quick update is that my house purchase didn't work out (in time), so I found a rental(with great difficulty) but I made it so nice and lovely and the freedom to take all my own decisions about everything and having the place to myself and myself and the kids is absolute bliss.
STBX is acting very badly a lot of the time (for instance hiding the kids passports preventing me from going on a holiday abroad) which helps me not to miss him and just be relieved I'm out of his madness, but in spite of that I still sometimes (esp when he is suddenly doesn't present as vindictive and power-playing) get pangs of sadness that it was impossible to make "us" work. The sadness is very weak compared to nearly excruciating pain it was about 18 months ago. It so happened that I have to pass my old house nearly every day on way to town or schools - something that I was desperate to avoid but literally the only available to me rental in the end was on the same road but further out of town - and the evidence of my progress is that I can walk past without feeling in any way emotional!
A year ago it seemed unthinkable. The feelings take a while to process, I try to practise self-awareness and do practical things like engage in therapy, do meditations and journaling to help myself process all the feelings connected to the separation, it helps me to move on quicker. I still dream about STBX a lot and I would rather not, but I know it's normal, that how our mind deals with all pressing issues and I just accept that these dreams would continue for a number of years...