This sounds so incredibly stressful for you and understandably so. I really feel for you so much as your fears begin to play out. Fearing your husband may always be financially and emotionally immature is also understandable.
As you'd already know, based on raising kids, there's a need to develop or mature emotionally so as to serve our children's needs and what's in their best interest. Having been married for 22 years and while raising 2 kids of my own, I've found it's not just about maturing for our kids. Developing emotional maturity in order to best serve the relationship with our partner is also important. For your husband to refuse to feel your fears, feel your need to develop financial compromises, feel your strong desire to maintain a sense of financial security etc is self serving. It sounds like he may only be feeling his needs and desires. I'm wondering whether he's fully conscious of the financial income and outgoings or he needs to be made conscious of them. I can recall much earlier in my marriage, after having our first child, my husband's mantra of 'It'll be right'. He couldn't relate to my financial fears or concerns until I put everything on paper and we went over the finances together. He was shocked and, in seeing how things actually were in reality (as opposed to in his imagination), he changed his way of managing money. He admitted to this being the wake up call he needed. We both were never really forced to manage so strategically until this point in our lives. Based on your own circumstances, especially as a single parent, you've always been fully conscious of the need to manage strategically. You've practiced financial management for years.
I suppose the question is 'Is this a major first time challenge for your marriage, one that you can both eventually rise to meet together, or is it his intention to always be completely carefree with the way he manages money?'. I suppose there's only one way to find out and that involves asking him. If he admits to never wanting to change, as opposed to reaching a compromise, then I'd be seeking legal advice so as to see exactly where you stand.
If you're willing to compromise with budgeting for certain luxuries, he should be willing to meet you half way.
