The advice about validating the 10 year olds feelings was great too, she does on the one hand need to be told yelling, banging fists on tables and throwing things is unacceptable but also asked why are you so angry and upset and allowed to vent those feelings but perhaps in another way.
My son had a powerful learning experience with this -- during the height of our divorce mess 3 years ago, he jammed a pencil into a kid's chest. Fortunately, the child was wearing a winter coat, but S12 had to be disciplined. The school knew what he was going through and did a great job helping him make sense of what was happening. The family counselor told him that it was ok to feel angry, but that he couldn't be aggressive. S12 didn't know why he felt so angry, and the counselor said that lots of people feel that way, and learning to know we're angry and tell people is a good skill to have.
Your son and GD are lucky to have you.