Cyberspace is a pretty great place to vent. Also, you can call me anytime.
I thinking venting your spleen eslewhere might be best for you; so you can focus on supporting him in the way he's chosen to deal. I'm guessing if there's was any possibility of changing her, he wouldn't have needed to divorce. I absolutely detest the phrase 'it is what it is.' (it seems to be my new boss' favorite) But accepting what is certainly seems the way to peace. There are some things I don't yet feel right about being peaceful about. But other people's people? That one I kind of have to let go.
It might help to wonder what it is that makes you so very nutted up. I know, you love TGIB, and want everything good and wonderful for him in his life. [I'm reminded of another story, which I hate when people offer to me when I'm nutted up....but it is what it is
The guy who helps the butterfly out of its chrysalis, because he sees it struggling, and then, a short while later, the butterfly dies. The butterfly gains its strength to live during its struggle. Without the struggle, it doesn't develop what it needs to fly.
So, what is it in you that needs so much to end his struggles?
y'know, or not.