Been there.
In my case my ex did take me to court but then his sympathisers wouldn't have been fooled if he hadn't.
At various points I've had the opportunity to (and taken it) to prove to them he's NOT the victim he made himself out to be.
I made the mistake of pushing for regular, sensible contact which he often flaked out on.
In hindsight (that being perfect vision) I should have just let him keep flaking and gradually disappear out of dds life earlier.
Instead there was intermittent contact. I bent over backwards to facilitate, when dd was old enough to sense what was happening herself she made a decision she didn't want to see him unless he made the effort to arrange contact without needing nagged and organised into it! She was old enough imo to decide that & so that's what we did. I sent him one link to her school holiday dates which he acknowledged receiving - he's not made arrangements since, not once. He barely even contacts dd remotely now, 1-2 times a year if that.
Dd is very hurt. He blames me of course!
As I say I regret it, the minor exception to my regret being at least dd knows I did as much as I could. And I appreciate that.
One time - on phone to her - he even 'threatened' to send her all the 'evidence' of me stopping contact over the years. Dd let me know that's what he was saying during the conversation without his knowing - I let her know 'fine tell him to crack on and send it you, cos it won't show what he claims' so she said to him 'ok send me that' and he back pedalled! Unsurprisingly.
Honestly, my advice -
Let him take you to court - it's not cheap and judges aren't stupid! Several judges saw right through my ex (he took me back to court every time I wouldn't rearrange to make up for his flakiness claiming I was 'preventing contact') I had a good lawyer plus as you're being advised I kept all communication re contact in writing.
If he doesn't - which is a distinct possibility that he's all hot air! Let him gradually fade out of your lives. Your DC are still very young, better it happen now than later ime
Don't make arrangements for him - let him do the running, he's an adult! He's perfectly capable of making sensible arrangements for contact AND STICKING TO THEM!
Don't wait around for him, if he's made arrangements and flakes - that's his tough shit! Do something else fun with DC.
Re csa - have they seen evidence he's not working? Have they checked with income tax dept of hmrc? If not they can and should! Unfortunately they do need chasing. If you're getting fobbed off by them contact your MP. Myself and others on mn have done this and it does light a fire under their arses!
Mrs clutterworth are you in uk? In uk courts maintenance isn't considered re contact at all, I wasn't even allowed to allude to it!!