M.K.
It goes without saying that physical violence cannot be tolerated or allowed. There is no excuse for physically or emotionally harming your child.
But this is a MUCH bigger problem than simply asking your husband to get control or be calm. Your husband is most likely grieving. Grieving over the fact that his son has special needs. Grieving that his son is not the "perfect" picture that he had in his mind. Feeling guilty that he does not feel the easy, "automatic" bond with your son. Feeling very angry (at God, at the world, etc.) that your son has these issues. You may have gone through many or all of these feelings too.
As for the marriage, you are both dealing with the situation in different ways. And it would be very natural for you to feel angry that you husband is not "loving" you son "the way he should." This will cause some of the greatest stress in a marriage. But know that all of these feelings that you and he have are *very* normal in this situation. Now you need to find a way for all of your to cope with the issue so that you can all be healthy.
Even though many men are often not big talkers, your husband may need a chance to deal with his feelings. Is it possible to talk to him about it? Tell him about some of the "not so nice" feelings you have experienced and give him the opportunity to agree/talk/etc.
Does your son have a behavioral therapist that helps you figure out how to better meet your son's needs? If so, it's time for you and your husband to lean on this therapist and get help for the entire family unit. Have therapy session every couple of weeks with all of you present (not just you and your son.) If your son does not have a behavioral therapist, it's time to find a family therapist that has experience working with families & children with special needs.
Please know...it's very easy to judge this situation if you do not have a special needs child at home. Do not let anyone make you feel worse about your situation. It's already bad enough. But other families go through this too. Do some online searches to find parent groups for families that have kids with similar special needs (www.meetup.com has tons of groups). They usually have message boards and you can talk to them about these issues.