I split with my extremely abusive partner when my eldest son was 5 and my youngest son was one. The damage to both of them is still evident, yet he never lay a finger on either of them. My eldest son, ground his milk teeth away with worry and frequently wet the bed if he saw his dad, or was faced with any kind of confrontation. You need some relationship counselling or split, and keep it amicable. Two years on from our break up and things are just about coming together for me and my children but thats because they haven;t had to deal with their father and the way he treats me in front of them since may.
Social services can intervene and have your child put into care if you continue to put him in this situation.