Just one other thing.
When I said you will look like the "bad guy" if you are not open about what is really going on, that almost sounds self-serving.
What I was really talking about is about them, not you. I know you are throwing yourself under the bus here thinking it is the right thing to do.
In doing that and allowing your children to have growing resentment, you are pushing them away to him. He really couldn't plan that better could he?
Even if that isn't his main objective (maybe he just likes making you angry and uncomfortable, but his motives are beside the point).
If you don't address this now, you run the very big risk of having no relationship with them later on or just a distant/mostly negative one. That hurts them as well as you. It's not allowing them to be close to you, to depend on you for honesty.
Being stoic here is not in their best interest if you want to be close to your children.