Do not pay him or give him any more personal or financial information. Once you start it will never stop. Do call the police. Blackmail and revenge porn are crimes. Learn from this unfortunate experience, and stop sending anything over the internet that you would not be comfortable putting in your front window. Good luck.
You can go to the police and they can choose whether or not to follow through with an investigation, or you can try to obtain a restraining order against the person (but he would have to be personally served)