What should I do

I'm 30 and my life is kind of stable (job, house, partner). I'm gay, cool with it and been living with the same guy for 12 years, almost. This summer I met some friends I've known for half a dozen years. They both left the region where I live for work and came to visit for some days. One of them knows fully well that I'm attracted to him, but I've got someone.

After the party that guy insisted we stayed together. He told me he was bisexual and that he'd recently became cool with it. Thing is he's engaged to a woman. The more the evening and night dragged on the more frontal he got, to the point that he began flirting and we kissed, many times. I refused to go anywhere further than that, I don't consider kissing as sexual so for me it's nothing like cheating (I know some peolle won't agree but that's how I see it and other than that, I've been faithful to my partner). But he wanted to. He wanted to go way further than just kissing. I refused. He told me how perfect I was, how smart and beautiful I was but I didn't want to do something I would consider as cheating while he was clearly intendig to cheat on his gf.

After that I tried to get in touch. Although he answered every single time I tried, he did so in a way that didn't engage conversation. I began to hate him for not understanding what he wanted. We could be friends, why aren't you acting like one? Thing is he only gets in touch when he needs something, like a ticket for a concert, arguing he didn't have a dime and would pay me back (he doesn't have a choice if he wants the ticket so getting my money back is not the problem).

The issue, after weeks and months of an emotional desert, he went all "I love you so much" a d "I could kiss you right now". He knows fully well that this is double language, not just a metaphor. I don't like him, he's a bad person, and a manipulator. But it seems I can't get him out of my mind even though I hate people like him... but I'm attracted to him anyways. Despite him being with a girl, I feel deep inside that he's gay and that maybe my "role" is to help him realize that.

Also the evening he flirted with me he noted how young I looked. I'm 30 but it's true that I look 16. It's part of who I am so in his case, I didn't react but in retrospect, I think I know why he said that : he's into males, yes, but young, and probably even underaged. Yes, it's exactly what you think. His following young gays on Instagram is kinda telling I think... no? I mean, I wouldn't do that... I feel I was the object of that deviatory behavior that night and I can't just blot him out of my mind and life.

I talked about him to my partner, was as honest as possible and he wants to help me but there's nothing he can do. The closest name I can give to what happened to me is an emotional aggression. We met again a fortnight after that evening we kissed. He was with his GF and wanted me to meet her. He also wanted my BF to join. I began to realize how much of a sickf*** he was.

And another "emotional aggression" happened again recently after I bought him and his girlfriend tickets. I'm hypersensitive and very altruistic, two adjectives that the guy uses to describe himself, though it's nowhere as close as I am, perhaps even a lie to victimize himself. Refusing to talk about what happened, making me promise to keep his secret, evading conversation anytime I try to engage it... I need him out of my life. I want to stab him in the back (figuratively ofc) but vengeance is not a solution. How do I get rid of that guy for good?