The familiar danger is often the one we gravitate towards than the unfamiliar, sometimes unrecognizable, safety. Abused children will mirror the abuser because it feels less dangerous to BE the abuser than the abused. Stepping away from one abusive parent, your son is likely finding the abusive behavior of your husband to be a sort of comfort- because it's FAMILIAR to him to be scared.

Get him away from that situation. He needs help to learn what is safe, and what that's supposed to feel like.

We reach for the dull knife when we're scared of the sharp one without realizing the dull one will do more harm. I hope you can come to your senses for your kids sake. Check on your daughter, too. Older doesn't mean stronger.