Ok I 100% get this. My kids have an equally shit father.
But your problem is that you want him to see the kids more than he wants to see them and he KNOWS this. So it’s become a control battle - he is doing all this because he enjoys upsetting you MUCH more than he wants to see his kids.
As a PP said, he hates you more than he loves them. That’s why he’s happy to involve them and manipulate them by using them to send texts - so he can prove to the kids that he is right and you and wrong.
Im afraid you need to accept that you can’t win this control game. You can’t make him see his kids. The court can’t make him see his kids.
So unless all these things you are doing ( meeting him half way etc ) and court mandated then you need to stop. Just drop the rope.
Send him an email saying that the current system isn’t working and lay out what you are proposing instead. Or better still ask him what he proposes. Tell him that meeting halfway doesn’t work for the kids .
Id run it by the experts here on Mn first. Ideally you’d use a lawyer but I know thats expensive.
Make sure its very polite and reasonable and talks about the welfare of the children and NOTHING about what suits you eg you need a break , you can’t make plans for the weekend
All comms need to go via you and not the kids. Tell him you won’t respond via them and stop doing so. This is a reasonable request - I assume he has your phone and email.
If he chooses not to do that then that’s up to him , but there will be no contact.
Don’t tell the kids what the arrangement is until he has phoned you to confirm he is on his way. Otherwise its too distressing for the children because he lets them down.
He needs to pick them from your house. His police paranoia isn't reasonable..
Or you can arrange to meet as some public place , like MacDonalds or a shopping centre . . But you don't tell the kids that you are going until he has confirmed that he is there( assuming you chose somewhere within a 20 min journey, so he needs to wait 30 mins or so ).
If he leaves before you get there then then at least you have tried. That will two Reasonable child centred options you have tried which he has refused.
Or he needs to pick them up from school on his nights. They don’t need any stuff as he will have their clothes and toiletries etc at his .
If you want to do half the driving it would be better that he takes them to his house for the weekend and then you collect them ( having phoned the kids first to check they are at his house ).
This meeting half way thing is just a tool for him to mess you about.
Im afraid you also need to stop trying to make him co - parents eg trying to get his to agree to the assessment. You don't need his permission and he’s never going to pay for anything that you want so you might as well forget it.
Of course it’s unfair. Of course the kids deserve better . But you can’t make him a better person . The more you push him on this, the more he is pulling back just to spite you.
You have taken on about 90% of the responsibility to make contact happen. You need to step right back and let him do the work iIf he wants to see them.
Always be polite in writing but don’t solve his problems .