My situation is a little different but I wanted to give my thoughts on this matter - I'm not married but fully vested in my SO for the last 9 years (marriage will come, we're in no hurry). Although we keep our finances separate, I am fully supporting her right now as she goes back to school full time. We are living on about 22K/yr for the two of us, which isn't a lot, but I do have to ensure a splurge now and then to keep things happy. New jeans, some throw pillows, going to see a couple movies during the summer releases... Little things I'd rather not do, or would rather do without that she 'needs'.
I think the thing to realize is that spending money is an addicting act. There's an endorphin release and a high when people spend their money and buy things; get things. Think of the euphoric high you got as a child when you walked into a room for of Christmas presents. Now scale that up to getting presents whenever you want (ie. luxuries you buy).
The difference I see between her and I is that she's on board with the IDEA of MMM, but she's still fighting with the addiction plus, since she isn't growing her own savings currently, it's hard to see the rewards herself. For you, it sounds like he's not even on board with the idea MMM, which is even tougher. I sold my SO on MMM by showing her a.) the financial security it'll bring compared to what a lot of baby boomers are going through right now and b.) showing how it maps to her dreams that she cannot achieve currently - working any job she wants, traveling aboard for extended periods of time and having our home wherever we choose, rather than where ever the job forces us to be.
An example of the addiction:
We were at the mall the other day to replace a pair of jeans and you could visibly see her trying to hold back from going shopping. That cute dress, this store is having a sale, maybe I could just browse the purses at Fossil, look at those shoes! It was a battle to keep her on the straight an narrow for our goal - a pair of jeans only. I ended up buying her a cheap shirt that was on sale as well to keep release some of the anxiety.
Its difficult some days but remember a relationship is about compromises and helping each other.
But seriously, my first compromise would be getting separate accounts. :)