My question involves landlord-tenant law in the State of: Massachusetts

I am a 21 year old pregnant female who subletted a room in my house, I accepted $1600 to move in (first and last) it has been about 3 months of them living with me and I am no longer working due to an injury, my father has taken over paying rent. He wanted the roommates to leave. I sat down with them and explained the situation, and at that time gave them a month and a half (now two months) notice to leave. They are now 10 days into March and still show no signs of leaving. They now owe $800 for February since that was NOT the last month. They have made verbal threats of harm to me and my unborn child, to which I have reported to my local police. They are now contacting my father and mother with all sorts of lies and "complaints". They have made me feel unsafe in my own home. Everytime i am home they threaten me verbally or threaten to call the police with a false claim. They are now saying that they were "scammed" and are demanding the money they moved in with back $1600, or to be served with formal eviction papers. My fear is that if we serve them with eviction papers, they wont leave and will still be in my home. As is they are not paying rent, and my father is paying rent for a house i don't even occupy for my own safety. I want desperatly to be able to go back home and decorate that spare room they are in as my sons nursery, i want to get back to my own life. My question is, should we offer to pay them the $1600 if they are out by a certain date, or should we move forward with the eviction process in hopes that they don't end up staying for many many months?
Thank you!