I agree with above.
An abusive fxxker.
His "you win", gives you confirmation that this is a game.
A game he is playing to get at you, using his children.
He cannot bear that you have free time.
He cannot bear that you are not under his thumb.
He cannot bear that you aren't working or consumed by the family under his useless gaze.
This is difficult OP, I do understand that.
But you need to get with the programme and stiffen your spine to him.
He is a lying manipulative fxxker.
Those hidden bank accounts is who he is.
Keep reminding yourself of what a duplicitous prick he is.
Do not collect the children.
Do not manipulate the children.
If he returns them, fine.
You need to inform the school and your lawyer of what the children are being put through.
But you have to see this out.
It is a game, he will use ANYTHING, including his children to win, even telling you that you have won.
Don't get sucked into this.