"Italiangreyhound It’s not that I see it as another chore - it’s that I seem to have developed a real aversion to it. The thought of it makes me feel genuinely distressed."

That is kind of what I thought, mine was more lack of interest but yours sonds like a real aversion. That's why professional help would be better than simply hoping it will go away.
It sounds like the burden of employment is on you and maybe also the burden of thinking about your child/worrying/planning? Can your husband work, or work a bit more, so you work less?
I wonder if there is resentment in your marriage, due to the problems of having a disabled child? Your high work load? Your husband's unemployment? The lack of sex? Lack of communication?
Is the choice to not have any more children mutual?
Again you do not need to answer these. I just feel there are lots of issues.
Some couples may find solace in each other and I'm a physical relationship, but for you both it has gone the other way.
I think you both need to 'heal' from the past traumas and face a future together where you each put each others needs high on your priority list if you can.
This means facing any past trains from a relationship that was abusive, the high pressures of a disabled child, and any issues that have developed between you both. I am sure you know all this but maybe it helps to see it all as a big picture. Not just loss of libido but something bigger. It may involve your dh communicating more and maybe even earning more as well as addressing your very real and obviously, for both of you, very distresssing feelings around sex.
It's not just about his sexual needs but the needs of you both as a couple.