He's 9 though, he's of an age, developmentally speaking where he'll display anger more.
I've been battered myself. I divorced with 3 young sons.
It is important that your son treat you respectfully. Not that kids are not their own persons and will try to push boundaries by pushing buttons as they try to get their way.
It's not easy. Yes, you have what you have, at the same time he needs to know that it's not open season for himself.