I am sorry for what you are going through.
My DS has no official DX but it has been suggested he could be lower end spectrum for a number of things. His Dad found it very difficult to accept that DS wasn't merely being will full and deliberately making our lives hard.
The things he said and did to DS, the way he treated him (and I am the first to admit, I didn't find him easy at times and he has frustrated me beyond belief sometimes), the way he spoke to him lead to a spiral in DS's behaviour to a point where we had a living hell.
I am not saying you should leave your DH, (sadly we split up) but on top of the problems he already has, the devastating effect your H's attitude has on DS's self esteem is likely to make things much much worse, especially as he feels rejected by his own Dad.
Even now, we are in a tricky place as DS's Dad is half and half, DS was subjected to a minor assault two weeks ago and his Dad responded by suggesting we try to get DS to try and be less of himself as he attracts the wrong attention. His manner with DS is often loaded with negativity and implied criticisms .
I don't know how you can get him to link his own behaviour and attitude to your DS's behaviour, but it will eventually affect his relationship with his siblings as he becomes aware that the others are favoured, apart from his self esteem and relationship with his Dad.
In the right environment, children generally strive for their greatest potential and parents should be nourishing that environment, not making it one of discomfort and uncertainty. I am sorry banana.. I think you have a really tough choice to make I wish you well. x