You are young, and vulnerable. This guy has manipulated you by his threats and stalking, making you feel fear. But because you are a nice person who takes responsibility for your actions, you think you can reason with this guy.
I was the same as you, and my stalker eventually broke thru my patio door with a gun and tried to shoot me. I had sought the help of the police several times, but got little help. The night of the break-in, the police had even found him and told him to stay away from me. This made him even madder, and later he came to my house. My cat, of all things, kept looking around nervously, and that is what alerted me to his lurking outside. I went to the patio door, and a huge rock came crashing thru. I escaped out to the neighbor's driveway where he kept trying to fire the gun at me, but thankfully, it had jammed. The police arrived, and it was one of those standoff situations , but they finally subdued him.

Even after his incarceration, I felt somehow responsible, so I understand where you're coming from. Listen, you are in NO WAY responsible for this guy. He is a stalker, plain and simple. There is no reasoning with this guy from allowing him to talk to you.

I nearly lost my teaching job because of this. It was many years ago, but in today's climate, I'm sure I would have been dismissed due to the history of people arriving at schools with guns. If you are working, you should be concerned about this too.

Yes, I agree with the others here. NO contact, none. Go to the police. Are you living at home with your parents? If so, do they know what's going on? If they know, they too should contact the police. If they don't know, you should tell them. But lastly, an obsessed stalker who has behaved as you are describing will stop at nothing, unfortunately.