Well...I made it through most of that first post...and yeah, pretty heavy shit.
That said...you come to a point where you just cut loose and move on. Yeah, I know, the kids are always the bond, but still, mentally and emotionally you have to cut free and move on.
This is why I stayed single after my first ex, which only last about 2 years total. I knew within the first 6 months that I had to cut loose from her and that it was a mistake marrying her...though I even gave it a second try during our separation, just to be sure I was being as fair as possible...but I took steps to get the legal process going anyway, as I was sure it would end up in a final split...which it did, and we split pretty much in agreement, so there wasn't any lasting hatred, and no children, but that experience made me see just how easy it is to get "trapped" in a situation that goes from good to bad and then proceeds to get uglier, and next thing you know, you spent 20 years with someone you no longer even like, never mind love.
I was lucky to get out quick and clean.
So it's now been 30 years, and I still have no desire to be legally entangled with anyone....and I'm still constantly being coaxed about "finding someone to settle down with" by friends and family.
I know that not all relationships are like that, and some are quite good...but most are pretty draining even if you manage to hang on to some kind of "love", and very often it's more about forced "duty" and "responsibility" that keeps it all together....but boy, that can be a pretty dismal environment to live in, never mind to try and be creative on any level as a musician.
So good luck...and don't beat yourself up. Cut loose as clean as you can...and make her just someone you use to know.
Don't even hate her...'cuz that makes you still involved emotionally. Just clear her out of your mind and move on.