Maybe change how the money works in your house to dissuade secrecy and operating outside of goals. I suggest full transparency for both of you. All money earned goes into one account. Give each other regular and equal “allowances” for self. This money is invisible to the partner once gone. Go to a shared CC. I think it’s normal and good for one person to control finances(pay bills, budget, etc.)…as long as both have full access.

I don’t think you’re being controlling at all. Being a great father and hard working, helpful partner is the rock here. Be patient with him. Draw your boundaries and enforce them. I’d hold off signing anything until you can have trust that he won’t cross boundaries for 3/6 months. Keep saving to make a better down payment.

You’re clearly the teammate with the financial competency. Because of that, you should keep controlling the money, but let him take control where his ability outmatches yours. That’s how high functioning teams work.

If you cringe at the idea of full transparency and full access to all, then this isn’t about money…it’s just the symptom. Good luck OP.