My exh is like yours OP. I didn't find out about the full extent of his debts until we lived together. The crazy thing was that the more money he earned, the more debt he got himself into. Like you I took control of the finances, we paid off the debts and while we were married it was all good because I was in control. He was so envious of people with 'better' than him and was materistic, which caused many rows because I wouldn't waste money.
When we split up there was savings and walked away with money in his pocket. Before the divorce was finalised he also got an inheritance, which I didn't make any claim on because it was for him. Just like your DH He blew the lot in around 10 months, just fritted away with nothing to show for it, but he got more loans! I don't know what was in his head, maybe having tens of thousands of pounds in his bank made him feel wealthy, so decided he should have toys like a brand new motorbikes which he got on finance. When I got wind of spiraling debts and all the inheritance had gone, I panicked because his name was still on the mortgage and I feared I would lose my home if creditors wanted to get his share. He did me the big favour because I bought him out and now own it on my own.
So now he has more than a double what his inheritance was. Did he learn? Of course he didn't!! He did exactly the same again and in under two years the lot had gone but he'd got more debts. His landlord had to take him to court for not paying his rent, numerous payday loans, borrowing money off DCs (before they worked it was birthday/ Christmas money) He used and was entitled to a food bank. I insited my DCs bought him food shopping rather than give him money. He laid so much emotional guilt on them. He refused to get rid of the motor bike, he started smoking and owned a car, on finance of course.
He's always worked, he is a hard worker and has earned a good salary but has nothing to show for it. He is so bitter and angry with me because I own my house and has said to DCs and anyone who will listen that he was done over by me with the house. He never paid me any maintenance after the first year, never bought the dcs anything.
So today 9 years later, he's got a good job, I don't know how he's financed it but he drives a sports car. The week before my ds's birthday last month, I found out he'd bought another motorbike (the last was finally repossessed) he'd borrowed money from my ds and for his birthday he gave him the grand total of £20 😤
OP, he'll never change, he'll never learn and you will spend your life, working and scrimping just to pay off his debts.