this is a bit harsh. you've got no idea what conversations they had about their financial set up, and whether any agreements they made have been stuck to. Several people have asked OP but she hasn't answered.
Perhaps when he agreed to take out the original 0% loan OP said or gave the impression that it all/more of it would be paid off by the time it came to an end.
Perhaps he has now thought about it and decided he would prefer to cover more of the household expenses, or that they should both try and drastically cut down on expenditure so OP can put more towards the debt.
Perhaps he just wants to discuss their options rather than OP unilaterally deciding the debt she accrued is now a joint expense that he is obligated to put in his name without any discussion or gratitude?
At the end of the day, even if he earns less than her, if they weren't together there is no way OP would have paid off as much of the debt as she has - both because she wouldn't have got the 0% deal (apparently, although as pp's have pointed out it's odd she can get car finance credit in that case), and because she would have been running a whole household on her own, which is still far more expensive than sharing expenses with someone else, even if it isn't split 50/50.
We don't know the details because OP hasn't specified, and the DH hasn't had the opportunity to put his side across at all.