S. - OK. I feel your pain. My husband helped out around the house when I had the first child. Then we had twins and all that fell by the wayside. The twins had special needs (one with sensory integration dysfunction, and one with PDD) so I know how hard that is. And, we've fought many a similar battle. I can't speak for you husband, but I can tell you what I've learned.
1) Try to truly understand him. My husband extricated himself from the parenting when it got really hard. And, he did not feel capable of working with our special needs kids. Honestly, he couldn't even really allow himself to think about it, or he would get emotionally overwhelmed (worry). As the therapy bills mounted, he felt a ton of pressure to focus on his job, and to bring home the $. And just the pressure of being the sole provider was a lot for him. Now, did understanding this make me excuse him from helping - NO! But, it did give me some perspective on what HE was struggling with and why he maybe acted that way. I then didn't see it as a character flaw, but as something we'd need to work through, so I could get my physical (I needed a break - I was exhausted!) and emotional needs met.
2) Get him to understand you. The idea to give him some time alone with the kids is a good one. Give him a few tips and head out for the day. My husband used to come home and complain abut a messy house (not even that messy) and I'd be home with 2 -2 year olds with special needs and a 4 year old (all boys). Then he'd say he wasn't helping because I should have done it during the day! In my case, I not only left him home, but he got the full routine - do therapy in the home for 2-3 hours, drive a hour away for therapy, get in at least 1 hour of 1:1 time with the oldest AND clean the house. He came away frazzled, missed an appointment, and the house was a mess ("Everytime I clean, they just wreck another part!") So, that day definitely added clarity to the situation. He admitted that he thought I never cleaned, and now he coudl see how hard it was.
Beyond trying to build some empathy, though, I also suggest that you try to talk to your husband about how he feels about your son's disability. And, also try to get him involved there, if possible. Getting him to really understand things from your child's perspective and to able to be there emotionally for you as you go through this, is important. That's what makes a team. - mutual understanding and support.
3) If you can't do all this on your own, get some counseling. My husband and I went through about 3 months of counseling in the beginning of all this, but were headed for trouble again after a few years. The pressures on both ends can overwhlem. We were able to work it out ourselves this last time, but it took lots of communication, honesty, and REAL feelings. At first, my husband would just say what he thought I'd want to hear ( or say something really insensitive). Now he knows that doesn't get us very far.
I wish you the best of luck. Take care of yourself, too. Make sure you get some time off. Being a mother is so hard. Being a mother of a child with special needs brings it to a whole different level.
R.