All I can suggest is that you keep your anger under cover for the sake of your son so you don't inadvertently create in him negative feeling about his father. Children deserve both their parents and should be allowed to have their own, uninfluenced relationships with them. As far as dealing with the anger goes, keep in mind that as long as you permit it, your ex is controlling both you and your emotions. Figure out what will make you happy, set your sights on that goal and work toward it. Anger, rancor and animosity should not be a part of that equation.
Exercise is a wonderful way to work through stress and anger.
So, too, is meditation. Just tell yourself that you are in control of your destiny and the rest should come easy. He left me and our child with no emotion no discussion no alternatives. The worst part is that I was emotionally devastated and he was angry now he is no longer angry but wants to get along and be friendly and I am not over the pain. I don't think at the rate I am going I will be able to move on.