Oh how awfully funny it is to throw rocks at the OP...
Stop arguing, start parenting together?
Put your kids first?
Sanctimonious and judgemental tripe.
Some dads take parenting seriously, collecting on time, listening to what's needed and making sure it happens. Observing school rules and policies and actively finding interesting things his kids want to do.
Others don't.
My DS dad has lived abroad for the last 6 or 7 years. he popped back the year before last for the first time in over 5 years. He drove through the village i live in TWICE without stopping off to see his son.
Eventually when he came to see him, and against my better judgement stayed in the house, I asked him to have him on an inset day.
I said to the ex 'he hates shopping, please dont take him shopping' go for a walk, kick a ball, cinema, anything. not shopping
DS said they spent the afternoon in Primark :(
Of course that pales into insignificance to the moment I caught him skinning up in the kitchen at 3pm one sunday afternoon while DS and I were in the sitting room next to the kitchen.
Then there was the time I'd begged for him to send some money for Christmas/DS birthday. Oh yes said Ex, I'm sending you £1k.
I went shopping, it was 4 days before the birthday. it took him THREE MONTHS to send the money. I put myself in utter shit because i believed him.
What I see is a mum here trying to do her best, and an ex who is an ex for a reason.
OP, don't bite when he texts you. Assume he won't contribute to anything and plan accordingly. You are 'lucky'... your ex is in the UK and can be nabbed by the CMS. Mine is abroad so it's up to him if he sends, and there is fuck all I can do about any of it.
I do confess to occasionally having sent long texts to my ex to point out how he is failing in the absolute bare minimum requirements of being a dad. That not bothering to contact your DS on his birthday is something they can't forget and Mum can't explain away.
Apparently, he's consulted a Dr (Google?), who told him he has Borderline Personality Disorder.
I admit. I went straight back to him with 'Trust me, you don't. I spent YEARS looking for reasons why you were such a vile and abusive monster, filled in questionnaires and read book after book looking for 'you'. the only place I found you was in the books about domestic abusers"
Text 1 - don't reply to him. You don't answer to him, his kids don't even want to see him. if forced to respond a 'Don't be ridiculous' will suffice.
Text 2 - CMS have this now. don't ask for anything or expect anything more than he is forced to pay by deductions. He doesn't need to contribute to parties, and actually its OK not to have them if you can't afford them. Or do a joint party with one of your DC friends if you know one of similar birth date?
Text 3 - your reply? I'll ask them Will let you know when they want to see you.
Then leave it.
Don't expect him to be the child care you need to rely on, don't expect anything and don't try to 'educate' him. Don't prevent contact, but don't push it either. Leave it to him to ask, and them to accept. Don't get involved.