Need Dire help

So for starters I'm 18(M) and my girlfriend is 20(F) We've been together since around October last year so around 4-5 months rn and I'd say things are going amazingly well There just seems to be 1 problem, her ex Her ex is a psychopath, she broke up with her a month before I got together with her. He would keep abusing her during their relationship compare her to other girls make really abusive and distasteful comments about her body, and my girlfriend, an angel or an idiot, depending on how you look at it, stayed with him for a year and 2-3 months. Although she wanted to breakup with him after just about 4-5 months he brainwashed her to the point where she felt breaking up with him is gonna be worse because Noone else wants her. (She's a bit of an emotional and an overthinker) Now I'm sure you would've heard about such issues before, but here's where it gets crazy. Both of us are preparing for neet, and her ex is in a different city, even after breaking up he keeps calling her from different numbers, from friends from family, and when she accepts the call just as any other unknown number, he starts abusing her, and she unable to control herself lashes back and it turns into a full blown argument for another 1.5 hour. This has been going on for the same 4-5 months We've been together even though she's told him she loves someone else. This guy is such a psychopath, at times he'll show up in front of her pg randomly or in front of our coaching even though he lives some 500 km away. Now by God's good grace coincidentally she has never been at the same place at the same time. They did meet just after their breakup and she's told me he tries to grope her kiss her forcefully etc. I told him that it's okay if he wants to meet and talk but he's gonna have to do it when we're present just so we can avoid anything happening or at least in a public place. But he's denied, he wants to meet in some random place ALONE. Now somehow he's managed to find my phone number my instagram account from fucking nowhere even though he doesn't know my name or has seen my picture and now he keeps trying to pester me. I haven't told my gf about him finding out my info because I don't want her to get stressed with just 2 months to neet Someone if possible please suggest a way I can take care of this mf without getting involved with the police because I feel that will take up too much of our time with just 2 months to neet, like I mentioned. I have some of his personal info, his number his gmail his instagram, what institute he studies in (JIST, Assam) things like that. Please I do not want to waste too much time on him but at the same time I wanna get rid of him