OP, in your place I would exit the chat.
Mute her number.
This will make it very clear that you are done.
I think you have done your best in a sad situation.
You are correct that you really need to depend on yourself going forward.
A man who would stand by a woman who would bully his child, and step aside from his wife who was defending his child, is not a man with a moral compass you can depend on.
His priority is himself and what works for him.
I think that history has shown this to be true.
It's not a trait, it is in his DNA.
He made noises to appease you but threw you under a bus the first chance he got.
He is not a good man.
He is a very selfish man, the type that would stand by and allow a coach abuse his child and not step in.
Your children will grow up to see him for who he is.
In the interim you are already losing respect and your love will likely be replaced with disappointment, sadness, distaste and eventually you will be repulsed.
Keep your family and friends close.
Keep working full-time.
I think you assertiveness will only grow as you mature and you will realise that this selfish man simply isn't worthy of you and your children.