How can I permanently stop talking to a weirdo without he threatning to commit suicide

I'm a gay male and last summer I met this guy at a gay section of a beach. We talked and exchanged numbers. He was very friendly with me but at the same time he was odd in the sense that he was sort of mentally slow, which I can detect in someone as soon as they say something. To make the long story short, this guy quickly became obsessed with me. He was texting me nonstop all day saying sweet things to me but in a weird way that just annoyed me. He knew I frequented very often that beach during the summer. As time went by, I was becoming more and more annoyed by him. One day he went to the beach just specifically to look for me but I didn't go there that day. Therefore he was showing other random men my picture amd my facebook asking them if they had seen me there that day. Someone that knows me texted me saying that he was doing that and that he showed him my picture to him also. I became extremely upset with his behavior and told him not ever text me again and I didn't want to see him or to talk to him again. This led to a big argument between us thru text and he texted me scary things saying that he was going to commit suicide, that he's not gay, that he hopes I'm HIV positive, that he was going to use drugs, and several other very weird and hurtful things to me. I freaked out with all of this but I didn't pay him any mind and blocked him. The next day after the argument, he went to the beach (I wasn't there that day) and he was crying there, crying hard and rolling on the sand and making a big scene there by himself with his crying (someone told me, I didn't see it because I was not there). This dude freaked me out even more. However, a few days later I ran into him at the beach and we talked and he apologized by what he had done showing my pics and I forgave him. I never wanted to date him and I was never interested in being in a relationship with him, in fact I don't even wanna be his friend but till this day I'm faking it that I'm his friend. Like I said before, he's mentally slow (not retarded) but slow. He usually doesn't make any sense when he talks and texts and says things that are just weird and have no logic. Now, my question is, I want to cut him off again because I don't want to continue faking friendship with him at all but I'm afraid that if I do so, he'll have another break down like before and that he might even try to hurt himself and I don't want anyone to do so self harm over me. It's a tough situation that I can't seem to get out of. I don't want to continue talking to him anymore but I'm afraid at his reaction if I try to cut him off again. What should I do? And is this dude retarded or what? Oh and another thing is that he's 33 years old (I'm 29) and he lives with his mother and his mother has to give him permission for him to go outside, WTF? What should I do to get out to get this weirdo out of my life? He doesn't seem as obsessed with me now like before but I'm still afraid of his reaction as he's highly sensitiv if I try to stop talking to him