My spouse has dementia and is convinced that he has not money. We have always keep entirely separate accounts; I am not on his checking; he is not on mine. We have shared expenses equitably - kind of. His expenses have run about 30% of his net income; mine run about 48%. Money is a BIG trigger for both of us. He is refusing to pay our estimated taxes, so I have paid those. He is now refusing to pay our property taxes, which is currently due as well as house and car insurance (these expenses are part of his 30%}. He is actually pretty well, except for understanding of numbers - consequently this idea that he has no money. I cannot absorb all expenses and am becoming quite resentful. Our trust does provide that I would have financial POA, but I don't think I have enough to try and invoke that PLUS he would know and it would likely create further tension. I am unsure how to approach getting him to pay his share.
You have here a man refusing to pay his taxes.
Life doesn't go well for people who don't pay their taxes.
I would see an Elder Law Attorney either with him or without him. If you can't afford this, then you are going to be in a whole lot of trouble eventually.
Executive function is CRUCIAL to protection and safety. You may need to apply for a financial conservatorship. And it is definitely time for visit to MD and some testing. Because to be this crazed about money and otherwise well doesn't make a whole lot of sense on the face of it. Generally someone like this is not functioning well in other manner as well.
See an elder law attorney. Make it clear you are needing to buy and hour of their time to discuss options. Take all details with you.