Katie,

it sounds like you've allowed yourself to cross some important boundaries with him that are inappropriate and yes, confusing for a teenager. It seems he did fall in love with you, and yes, he is holding you hostage emotionally and is acting in unacceptable ways. What you need to learn from this is to have stronger boundaries.

It would be perfectly appropriate to reach out to a friend of his, tell that friend that his behavior is concerning and dangerous, that he has threatened suicide, and that you need to distance yourself because the relationship has become inappropriate for you and he is doing unacceptable things. Then I would block this person and not speak with him again. He should not be allowed to interfere with your friendships or relationships. And yes, the threat of suicide is emotional blackmail. So do yourself a huge favor (and him) and end the friendship.