'He wanted me to do a couple of things that I wasn’t comfortable doing but he pushed and pushed until I went along with it.'
What happened? Of course, you don't have to talk about it if you don't want to. xxxxx
'He also accidentally called me one of his admirers. And another time said that I was very easy to influence'
Ohhh, I don't like to call someone a narcissist usually as I think the word is thrown around too much, but this is classic narc, bigging himself up and putting you down etc. Who but a narc talks about having admirers?
'Another thing is that in the beginning he was full of praise and compliments about me. Then for no apparent reason he started negging me a bit. Now it’s like I barely exist.'
Hmm, IMHO, he'll be back, 'hoovering' you in. That'd be the stereotypical narc behaviour. Don't let him.
'Another thing is that he has a friend who did something that he disapproves of morally. He’s making it a bit of a mission to teach that person a lesson rather than just think that it’s none of his business.
He gets a lot of moral outrage generally. He’s not religious and not perfect himself.'
I'm no expert but IMO this may be some other personality disrder trait, Borderline or something, the desire for revenge. A lot of people (esp personality disordered people) have a mixture of different traits. Of course it could be 'just' another narc thing, his ego somehow feels threatened by this friend, and wants to bring him down a peg or two to make himself feel better. Is his friend more conventionally attractive or successful than him or something?
I think your instincts are right. He's already used his charisma/your vulnerability to manipulate you into doing stuff you didn't really want to. He could make you do something worse next time, or take advantage, or generally fuck you up. I would keep him at arm's length.