Ex-Wife's New Boyfriend and Me

So I've been divorced for about six months now. My ex-wife is a year younger than me, 27 at the time of our separation. We had a pretty rocky marriage with a lot of infidelity on both sides, but mostly from her side. She loved meeting new people online, and cheating was just part of it. I kind of got used to it after a while, and we made this weird unspoken agreement that if she wanted someone else, she could have them as long as we had no one else outside the marriage. It was an odd way to run things, but at least we were upfront about our desires. Anyway, I left her last year for good after a particularly nasty betrayal, caught her with her latest guy friend when she thought I was out of town visiting my parents. I felt like all trust had broken down and I couldn't take it anymore. Since then, she's moved in with this new boyfriend, Jake (they met through that same online chat app). He's about our age too. I've been doing okay adjusting to single life, a lot of time to myself, mostly just focusing on my studies now since work has slowed down after the divorce. But I caught wind recently that Jake is apparently hitting on me too through those same social networks. It seems he knows we had this arrangement before and is trying to seduce me with offers about how good things could be between us both. It's confusing because obviously my ex-wife still wants me, but she also clearly has moved on romantically already by living with Jake now. So there's this tension of knowing they're together in person while he tries flirting with me from afar too. I've told him to stop messaging since it's not something either one of us can act on right now given where things are at, but it still feels strange knowing my ex-wife and her new boyfriend are both trying to get back into the mix. I know it's immature, but part of me just wanted to throw myself between them physically when I found out. I guess deep down I'm not ready to let go yet, but I have no idea what an okay way forward is anymore either.