You're very perceptive, Pralines. He's a lucky man!
I will have to stay out of the "what to do" side of things because I've got ishoos with money, too. I'm fantastic at the big stuff - making money work, optimising interest deals, and so forth. But, to me, "finance" is kind of abstract - like optimising a business budget - whereas personal spending is a shambolic mess of misplaced emotions. I am currently extremely poor and scrape by on a poverty budget. It's probably good for me (said through gritted teeth.)
Before things went tits up and I got therapised, I was aware that I used spending as a substitute for love, self-worth and confidence. But, it seemed, whenever I discussed it with my pals, 90% of them were the same. After all, our society encourages it; you only have to look at the not-so-subtle messages in advertisements to see that! Difference, for me, is that "Because I'm worth it" didn't refer to a treat so much as a basic need. When you feel 'worthless' the suggestion you can buy some 'worth' is seductive ... even when you bloody work in advertising and know what's going on 
It's eight years since I completely crashed and burned. Ten years since I booked my first therapist. I spend less in a whole month, now, than I used to spend on lunch with the girls. The week before last, I bought £180 worth of things I "needed" but could have lived without. On poor people's credit (39%apr, will be around 150% in reality by the time it's paid.) My finger hovered over the checkout button for THREE DAYS. Eventually I caved. I admitted I was feeling very down, lonely, etc, and I admitted I was acting out. But I still bought ... and still feel good about my purchases

I can probably admit that last part thanks to the therapy. The 'old' me would have felt dreadful, weak, worthless ... and we all know what I did to fix that feeling, don't we? It's called retail therapy for a reason!
OK, so there I've added to your confessional replies about what this behaviour feels like and how deep the issues are. I need to point out to you what seems obvious: When you and H got together you rescued him, yes? I mean, I'm sure it was more than adopting a sad dog, but nonetheless your relationship was founded on your being strong and sorting him out.
If your getting married was conditional on his getting sorted out, I'm afraid that was grossly unfair on the BOTH of you. Even worse, it meant you were both signing up to a relationship which you did not have.
I need to ask you (both?) to have a good hard think about that.
Oh, and Mr Praline - Write yourself two very big notices! Keep them in front of you, and make mental copies even bigger! [1] If I can afford that, do I want it or need it? [2] I am spending instead of feeling. Take time out.
Good luck, both ...