When I split from my ex, some 25 years ago, at first we just had an arrangement between us that he paid maintenance to me for our 18 month daughter.
Then when winter came around she needed a new winter coat, and I was living on benefits, so I asked him to send some money for a coat for her. Which he promised to do.
Of course, the money didn't arrive, so I contacted him again, three weeks later, and his excuse was he didn't have the money as he had to have his home redecorated !!! As you can imagine I was furious, his daughter's wellbeing should have come before painting his bloody living room. So I contacted the CSA and got them to sort out the maintenance. He ended up having to pay five times more than we had agreed and the CSA took it straight from his wages.
He complained how hard up he was and I admit to taking great pains to point out that had he just sent the 20 quid for her coat, as he had promised, he would not be in that position.
So you are not being unreasonable and I would get CSA involved and tell him you are doing so. If he can't be arsed to look after his own child, then he'll have to be made to do so.
Useless Twat !!!
Good luck, Sweetie, you sound like an awesome mum.