You should call the police department again and ask to speak to a commanding officer or the precinct captain. Insist that an officer be sent to your home so you can file a report.
If you had given your son in law permission to move in, he cannot be evicted without notice unless he agrees, and most state laws force the owner to give at least 30 days notice.
However, your case is different. Because of the threats and vandalism, the police may force your son in law out of the house immediately in order to protect you.
Your best source of help will be local law enforcement. They wont take you seriously unless you are persistent.Speak to a police supervisor.
Also, I think the correct court for you to contact is New York City Housing Court. They have free attorneys available that can assist. See the website
A resource center is available at Queens County Housing Court,
89-17 Sutphin Boulevard, Room 235
Jamaica, NY 11435
There is also an organization that provides a Housing Court information line, you should call -9 a.m. to 5 p.m., Monday to Friday:(NNN) NNN-NNNN