To support my friend

[Bumpy23]

My friend is in a marriage with children. Call him A and her B.
A is my lifelong friend, we're practically family. He married B and it's been nothing but a nightmare. On the face of it, she's very nice a charming but she's wicked to A. Spiteful and unnecessarily horrible. He's a very present father, he adores his children and works very hard to support the family.
She's Always threatening to leave or divorce him. If they didn't have children he'd be long gone, but he says he can't leave and his children with her, he wants stay, put up with her unkindness and raise the kids and see they're ok. Once they're independent, he can then decided to stay or go. I have to be careful what I say incase of outting.
But aibu; to support him staying until kids grow up? Or should I encourage him to leave?

He realises he can still see his children if he leaves right? I mean even if she is as terrible as he claims and he's such a wonderful and amazing father even if she makes if hard a court would legally enforce something if need be. I suspect there's 3 sides to this mind, I'd not get involved but say I'm here if you need me.

He’s your good friend, you should support him in whatever decision he makes. It’s not a good environment for him or the kids but he knows that leaving is an option for him and, so far, isn’t planning to leave. That may change but whatever he decides he will need the care and support of people around him. The dynamics in domestic abuse often leaves the victim isolated from friends and reduces options to leave or get help. I’d hang on in there with him.

Yes,- absolutely. I've probably worded that wrong. I would support him whatever, but sometimes I wonder if I'm too involved to see it black and white.
He's not perfect by any stretch, but I can see that if stays, he's unhappy if he leaves he's unhappy not being with his children everyday. There's a history on her side, and it's heartbreaking. I think he hopes if sticks it out it might help her. But she just takes all her hurt and damage on him and the children. But it's difficult to quantify. It's things like embarrassing him by not passing all the info on so he looks daft. Emotionally blackmailing him.
I just want him happy- he wants his kids happy.