I’m sorry but you need to leave. He does not want to learn how to manage money better. Either he has a gambling problem or some other issue.
You are putting your entire life at risk here, I am not exaggerating. As soon as you marry, he’s going to consume every last dollar you make. You will never be able to afford a house, or if you have a house, manage the repairs needed. You will never be able to retire. A medical emergency will financially ruin you.
As much as you love him, he is going to pull you down into this tar pit and you are not going to be able to escape. Love is not enough here.