Tbf Garam hasn't done a single thing to fix anything thus far? On the contrary, he has repeatedly pushed Jaehyung away, and it's Jaehyung who keeps pulling back and trying several (argumentatively dumb) things to stay with Garam; Garam who again has done nothing but put distance between them. I will not say Garam doesn't have reasons for his attitudes but saying he is trying to fix things isn't absolutely one of those attitudes though. Also particularly disagree with your instance of Jaehyung not growing as a character, when the fact he wants people to know about his relationship with Garam is a HUGE improvement when talking about a guy who was the worst kind of homophobic, so there's also that perspective I guess!
I'm leaning more into Garam not having to fix things because they just don't work, and because Jaehyuk has been acting like the horrible asshole that hurt Garam in the past just because they fought/broke up. The moment they're not together he starts treating him like trash?
Also they're both really bad at communicating, very immature pretending that the other magically reads minds, and they cannot be honest in the way the other needs it. Communication hasn't worked so far because they simply don't know what to say to make the other understand their perspective. Of course I don't think Garam is perfect either, it wasn't really my intention to defend him because he's also been a dumb ass (I wasn't saying that he has actually tried something, I was just quoting other comments saying that he should).
It's just that Jaehyuk rubs me off the wrong way, especially because I've been in Garam's position with a partner who knew very well I was in the closet and pretended they didn't care when I asked if that was OK.
I don't really think Jaehyuk has grown just because he wants to flaunt to everyone about his relationship. He just doesn't give a f about other people's opinions, even if it dismisses his own partner's feelings and traumatic experiences as a gay man.
You know what I'm remembering again that Garam didn't say anything all night and then got pissed because he thought Jaehyuk hung up and now I'm pissed lmao I really hope they don't get back together bc they just don't deserve each other, even though Jaehyuk is an asshole I guess he has his own way of showing his love but many of his actions were not it, as for Garam get therapy frfr he just cannot handle someone like Jaehyuk and Jaehyuk cannot understand his pov or force him to come out

Why is it Garam's job to fix things with Jaehyuk? Honestly, I'd rather they just didn't get back together. They're not compatible, they both suck at communicating, and they have lived completely different realities. But I understand Garam's perspective very well. He has gone through some homophobic shit and lived in fear of people's rejection and mistreatment of gay people. Even Jaehyuk was a horrible homophobic POS to him since the beginning and still dares to claim he "isn't gay", like he's not the same as him.
But Jaehyuk has never been through homophobia and probably never will, at least not to the same intensity as Garam. He's tall, handsome, somewhat charismatic (even if it's fake), and rich, stuff people love to suck up to. Some may criticize him behind his back but be blatantly homophobic? Probably never. He cannot understand Garam's fears because he is in a privileged position and he's also selfish. Besides, he's only nice to Garam when he got what he wanted, and the second they drift away, he treats him like shit and even talks badly about him. I didn't expect him to magically change, but he hasn't grown one bit either.