I've just read your posts, so sorry if I've missed other comments saying the same thing. But the problem is that finances isn't just this siloed thing that he can be a bit crap with or selfish about and then be a great partner in every other aspect of life.
Money affects so many aspects of family life so you need to be on the same page. I think you both need to sit down and make a joint budget with all your expenses and income and figure it out. If he won't then you could do it and ask him to look at it and see if there are any changes he would make.
If he will not co-operate with you at all on finances then it's relationship counselling or potentially a relationship ending situation. You say he buries his head in the sand about money, but you are kind of doing that about the relationship. If you are in relationship with someone who is happy to see you struggle whilst he gets treats, who would not pay important bills, who would reduce his contribution to the family to keep you in this stressed situation... that isn't a kind and loving person to build a life with and it isn't going to get better on its own.
It could be that things are just really tight for both of you and you are both sniping about it - the way new parents might snipe at each other about who is most tired, when really both need more sleep. But it does sound in places like it could be actual financial abuse, so definitely read up on that and see if it fits with other things.
I like to listen to The Ramsay Show (you can catch it on YouTube) it's a radio call in show about personal finances, and the calls are about situations like this. Whilst it is US based, I think there is a lot of transferable ideas about budgeting and relationally how we handle money. I think if you listened to it for a while you would have a clearer vision of what working together with a partner to improve your joint finances could look like. I definitely felt my standards rise whilst watching it!