I am confused why are you calling it a relationship, when it hasn't been for three years. Are you sure he has understood the relationship was over.
Not wanting to be with him Is absolutely is enough of a reason. It may help him if he knew why but that would involve engaging him in conversation, and he might try and talk you in circles.
Block him from everything.
Ask your friends to ensure they don't pass on your details.
Also see with work.
Review the stalking laws in your state.See if anything applies.
Apply for a restraining order.
Can you speak to his friends or family and express concern for his very unhealthy behaviour. Maybe they can reach him.
Really hope you find a solution soon,it seems a very long time for someone to still be confused about the status of their relationship.