I'm really disappointed on your behalf that you're getting nowhere with regards to FA and the relevant authorities. What's the point of these laws if they can't police them FFS?
With regards to the Prick's demands, you are going to have to grit your teeth a little longer and play the long game here. But please keep in mind that at the end of it you will walk away with financial independence, as well as your freedom and the respect of your kids.
So, submit to him your 'expenses', make it appear that you are dancing to his tune in that regard - BUT you are going to use this in your favour. Because he's absolutely coercing you by continuing down this track despite the fact that you have made it clear that it this anomalous, forensically freakish control of your family finances has caused the irretrievable breakdown of your relationship. It is exactly that documentary evidence you need for the Police, for the Mediator, for court. So send him all the detail he needs, and make sure you tell him exactly how it's making you feel in the process. He will never be able to deny what an abusive shit he has been when faced with the cold hard facts that you produced at his insistence.
I would also be inclined to tell him that since you are now very separated he can fuck off to the far side of fuck back to his parents for the remainder of his trip, rather than leaving you on edge with his comings and goings, causing further upset by his complete disinterest in your children.
And absofuckinglutely sell his golf clubs.