Lovely,
With some ex partners the reason they act as yours does is because they’ve lost you, have no control or are out of control themselves that they desperately try to find a way to control.
If he’s not paying when he should then contact the cms, they’ll help and advise the next step.
For what it’s worth, not all men are like this. Your ex and mine are, but after the time I’ve been apart from the ex I just dismiss his behaviour.
Take care
Jamiebear