You probably do need legal/police help. Sometimes all that is needed is a cease contact letter from an attorney.
Did your H send a short, concise NC letter? If not, that is probably water under the bridge at this point. Do they work together? He needs to find a new job. It took a year of looking but my H found a better job than he had. He had to chuck a lifetime of contacts and career building because he is now in a different career. We are both sad about that but he made our life hell and his crap has cost him dearly.
We had a predatory sociopath OW. Her notes, emails and gifts after DDay alerted my H's IC to give us specific instructions on dealing with her. First, very strict NC, no matter how many ways she contacts you. Your H must not answer her or engage her. In the IC words, you have to strangle the A by cutting all communication back to OW. You cannot control her, but you and H can control your response. Give her nothing. The IC compared her to a vampire seeking their life blood. They get desperate, it escalates, declines, and then they circle back again looking for just a drop. Do not give her that drop. The OW will see that as hope. Second, all emails, texts, notes, or gifts should be sent directly to you before they are deleted. No secrets. My H brought me the gifts and I disposed of them. He linked his email to me so I got them as he did. Emails sent to work email were forwarded to me. Third, present a united front no matter how hard it is.
It is hard not to engage. The OW shows up at places she knows we might be, including church services. It has been awful. We are moving to another city as soon as the house sells. I have not put my whole story on SI because I do not want her to find me here. I had an ah ha moment not long ago. Not only did she want to win my H, she wanted to see me lose. It is a sick game with some of these OW. As I have said before on SI, until you have been used by a sociopathic predator you cannot understand how an adult can be sucked into their crazy world.
You can absolutely be furious at the OW. I know you are hurt and mad at your H. While he did indeed start the A, there is no reason not to be angry at her. She is accountable for every action she has made before, during, and since. I do not agree that anger at the OW is displaced. While not minimizing my anger at H for the A, even MC and IC recognized the need for my anger at OW.