Your husband needs to learn a thing or two from your child.

Make sure your husband learns that you shoukd rule with respect, not fear. I believe that as soon as a finger was laid on him, your son became fixated on pride and protection in his own house. I've been there, it's not a good place to be.

I think you should let your son off of the hook for the simple reason that if you plan on punishing your son for his wrongdoings, you should be punishing your husband as well.

Oh, and make sure to calmly remind your husband that as he gets older and more feeble, your son will get stronger and wiser. If he plans on putting his hands on your child, he better be ready for when your child fights back.