I know this information can be disheartening. I am sorry you are going through this.
The definition of speculation is "an opinion or conclusion based on incomplete facts".
Maybe it isn't mind reading. But it is just as bad. The monsters are working overtime in your brain when you let that happen.
Part of detatching, is not worrying about why or why not they did something. Far too often, we imagine much worse than what is really going on. The only people that that hurts, is ourselves.
You are correct, his relationship with his children, is his to make or break.
