^^^Crimson, I am so right there with you. It's heartbreaking, and frustrating, and infuriating. All of it. Losing time with your kid, your WAS not believing in your capacity to change and having no imagination that you could have a great relationship and family together, their inability to change, their inability to accept their new reality of life after D (no, we don't get to just decide ad-hoc when we will take our child away from the other parent!). And, for me, blaming myself for choosing a mate so poorly.
Gah.
But it is what it is. And living in the past or "if only's" won't help us move on. Grieve for all you have lost-- you have lost a lot. Mourn it, feel it, be angry about it. Scream in the shower. Go ahead.
And then, make your peace with it. And move on. There is another (better??) life awaiting you. None of this is your choice, and you don't want it. But that is life. There is no making sense of it. It just IS. And all we can do is keep on keepin' on-- being the best we can be and living the best life we can live. And feel grateful for all the blessings we still DO have.