Unsolicited texts from someone in high school, uncomfortable

I'm a girl, I knew a guy from since school with whom I used to be friends but not anymore. He's from a good Christian family, we went to a Christian church, he's in our group of friends. He treated me so very nice but I became more and more uncomfortable hanging out with him because he kept asking me to join him in things I didn't like doing. He was kind of troubled and needy, too. There was one point where I wasn't sure whether he was into me romantically or not, but he said he wasn't. When I graduated from high school and move on to college, I stopped replying to his DMs on facebook.

But bottom line, this guy, like, doesn't know boundaries. I can't believe that he has been doing this for the last 4-5 years. Every few months he'd drop a line asking how I'm doing. Or "I haven't heard from you in a long time". Or just randomly say hi, hey, hello. Or ask me to join in activities that I don't like doing. I am sure I'm not the only one he's doing this with. He's just, literally, a crazy person.

I've been ignoring his texts for a long time until recently I just gotta have to click onto to the texts to see what he's been writing, and he saw that I read it and he's like "oo you read that", like he was teasing me.

I don't think he's gonna "do" anything to me, like stalking or harming or whatever, cause he's a "good Christian" but like, it's just annoying when he pops up. I don't really want to unfriend him on Facebook or whatever cause he'll try to contact me through email or something like that. I don't want to reason with him either because he will always reason back and have the last word. I just feel like he'll never let go, and I'm uncomfortable with that. Should I take any hard action or just let him be?

Thank you for your help.