DIFFICULT EX

[ZoeSusan]

I'm writing this with a heavy heart and feeling totally and utterly devastated.
My ex and I have 2 beautiful children together aged children together, aged 1 and 3.
We haven't had set days because he has been coming here whenever he feels like it to see the children (which isn't very often), maybe once or twice a week. I have put a stop to this as he has started calling me vile names in front of the children. He has turned nasty about this and said he will start having them every Friday and Saturday after this weekend. Knowing full well I work this weekend, a 12 hour shift on Saturday. I asked why he can't have them this weekend and he said it's because he is going to a local festival this weekend which he already has a ticket for and in his words 'you didn't ask me to look after them this weekend so I've made plans' 🤬
He hasn't seen them now for 8 days, and the last day he seen them (last Thursday) he called me a 'fat dumb c**t' in front of them and He hasn't made any contact asking to have them at all this week.
I said to him today that he hasn't seen them this week and thought he would be looking forward to having them for the day on Saturday, and he said 'well that's your fault I haven't been able to see them'
I'm really at a loss to what to do about this situation. I never wanted things to turn nasty and certainly never thought he would be this selfish. A lot has happened which he has turned around on me and he's displaying signs of very narcissistic behaviour. His family do not like me so I can't talk to them, and I just feel like this is very unfair. I have had to miss work before because he has refused to have them, saying 'I'm not your glorified babysitter to have them just while you're at work'. He hasn't given me a decent amount of child maintenance in 2 months because he's been emergency taxed at work and when I quizzed him about how he can afford to go to this festival but not pay for his children he said the ticket was bought for him as a present.
Any advice we come please. Thank you in advance. Am I being unreasonable?

You don’t babysit your own kids - tell him that!! If he can afford the festival he can afford child support. What a vile man.

Thank you. I feel like I'm just totally deflated. I have tried to do everything that is best by my children, and he just doesn't understand how I can think it's him being unreasonable.
I have a lot to pay out for being a single mum, and need all the hours I can get at work but with him being difficult I'm finding that hard work... my mum and Nan help with childcare in the weekdays but my mum also works and I feel like she is entitled to a weekend to herself, although she has started having the children every other Sunday because he is said he's working Sunday's now. I feel like he should have his children every weekend while I'm at work because this is the only time I really get to myself and I have the children the majority of the time. This is by no means me trying to get rid of them because I love having them, more the fact that he goes around playing the victim that he misses his kids, and saying I stop him from seeing them. If he missed them, wouldn't he jump at every chance to see them?