Venting and maybe some guidance?

I’m ending things with my long term bf this weekend and it kills me.

I have been dating this man for over a year. I knew he had some mental health issues, but I didn’t know how in depth they are. The short of it is, he needs help but refuses to admit that he needs it and thinks I’m overreacting. He is a good person. My best friend. I’m breaking up with him because I keep catching him in weird lies. Not cheating but more like making things up about himself. I made a post on here awhile back about it, but basically I got confirmation from several sources that he was lying about doing online graduate programs. He wasn’t enrolled at all but told me, our friends, his family and mine that he was getting a degree in a very specific subject that he showed no interest in prior. So that’s when I asked around, had some people do some research for me and sure enough, he isn’t. That’s not all. He also has been telling people in his life, in great detail, about events and friendships that he had that never existed. For example, he talks about these long distance friends that he has on a daily basis. I found out recently that they don’t exist because he’s gone as far as faking phone calls with them. Our mutual friends recently came to me and said that he’s been talking about “secret missions” that he’s been on with the military that don’t make any sense and don’t add up. Even his family is a bit worried. I’ve tried talking to him about it but he either says, “No it’s all true!” And when I ask for evidence, it’s, “Oh well, someone hacked my phone and stole all of the evidence.” Or he just straight up denies everything. He’ll even try to say, “Are you ok? You have a lot of anxiety recently.” There’s been a few instances where’s he’s conveniently had an “asthma attack” (he’s never been diagnosed with it) in the middle of these types of conversations. It’s sad and scary to watch because it’s almost like he believes the stories that he tells. I’m heartbroken and I’ve tried getting him help. I’ve wanted to stage interventions but I fear he’s too far gone. Yesterday is when I got the paperwork basically proving to me that he’s lying about being in online college. That’s the moment I knew it can’t go on like this anymore and I can’t live in a constant, “WTF” state. He’s the only person I have ever loved and I’m gonna miss my best friend. Everytime I think about what I have to say, I just start sobbing.