OP "Whilst I am aware that the current situation is not fair on DH and must be really awful for him, I really don’t think he would leave."
He might, he might surprise you if he feels desperately sad. I hope he will not, because it is better to work this out, better for both of you.
I've always said (in my head) my dh would not have an affair or leave. And he has not. But I would honestly I should not assume he never would. Because much as I love him if I was desperately unhappy, I think I may well leave.
We have two two kids who are quite hard work, but he is married to me and if he chose not to be married to me, that would be his choice. I would not expect him to stop being the dad of the kids.
I've had periods of not feeling very sexual at all, and it has got better over time. I don't want to give you loads of advice because I think your situation is more extreme than I have had, and I think you need professional help to deal with this.
But I am happy to answer any questions if you want. I actually think it is very common to go off sex as you get older (if you are a woman - I know this as I have spoken to women about this, I've not spoken to men so I don't know if this is so common for men).
But I really feel this is unfair. "For a husband to walk out on a wife when they have a disabled child together and the wife went through a severe depression for years arising from DC’s disability and is obviously having some psychological issues with sex and is trying to find a solution would be a pretty dishonourable thing to do if you ask me."
I think anyone can end a marriage if they wish to. It doesn't mean they will stop being part of their child's life. It's not dishonourable to end a marriage if you are unhappy.
However, you have said "and is trying to find a solution..." so that suggests you are going to try and find a solution and I think that is great and would be very good for you both. has the depression now gone or is it still part of life and have you sought help for this? A relative of mine has a dh who is depressed and will not seek help. I just to support her being supportive but now I feel frustrated he does not seek help. So I really hope you will.