It doesn’t matter what he os diagnosed with it doesn’t give him the right to behave negatively towards you.
No one here will be able to tell you why he is like this because there are so many things it could be that don’t have anything to do with ADHD as well.
It is wonderful you are looking to support him but make sure you are getting support for yourself.
My best friend of over 15 years has similar attitudes to your husband and also has symptoms of ADHD ODD and Rejection sensitivity. It has built up into alcoholism and physical abuse of his sister and friends, I had to go to hospital because he bit through my ear.
If his behaviour is getting worse and hurtful to you you need to get support for yourself and evaluate just what you are willing to put up with
Now for him refusing to do things at home, do you already have a division of tasks or are you the one cooking, cleaning and washing everything?
Because if you are I would refuse to do anything for him until he got a better attitude and was thankful for everything you do.
However that is just me, and if you think doing something like that will make your life worse and his behaviour worse I would seriously consider finding a psychologist or something similar for yourself.
Just because someone has ADHD/ODD/ect isn’t an excuse for bad behaviour and yes maybe you might need to accommodate them and support them in someways it doesn’t mean you have to be there doormat to spit on.