First of all you need to be strong for your son! Your son needs to be your #1 priority! You don't need that kind of man in your life & your sons life!
You can't just stop loving him cold turkey, only time will repair what he has broken! As far as forgetting, you will never forget, but you can forgive. I'm not saying go back to him, what I am saying so that you can begin the healing process, you need to forgive so that you can be at peace with yourself.
You need to take it day by day, go out with your friends, meet new people! Don't rush into a relationship. Enjoy being single!!!
You are on the right track by starting a new! Although, if your son is still under the age of 18 years old, your ex still has a right to see him under the eyes of the law. So, you may want to go to court and get full custody of your son. Be sure you document all the abuse he has put your son & you through.
NO man is worth your tears and one who is will never make you cry