Duuuude...

Yoon dude, just leave them both. You're a fucking great person who does a great job for society, you did that for the greater good, I know it's hard to understand that, but dude, if they're your family they should understand your life choices as an individual. Selfish? Of course it's selfish, but kneeling down to every single thing others expect from you is also selfish of them.
I can't stand Taejoo and how he acts as if Yoon's the worst human on the face of earth: he explained the situation, you redid your life with a different man (which is completely understandable), you rejected an ill person in the worst harshest way possible, and you even bent to your new boyfriend's blatant toxicity... AND NOW YOU HAVE DOUBTS? Oh no, man, that's not nice you see? Are you not ashamed in the slightest? If I was in you place, I'd not dare to show my face in front of him again, I would demonise him as much as possible in order to have a excuse to ignore him and not mess with our lives anymore...
And then the fucking boss. Dude get down from your pedestal and act as half the adult you pretend to be. You let him get closer and closer to then push him back, you get stressed because ya boi Yoon decides to be an adult and not continue a nonsensical relationship with someone who can't really put his feelings together, and you try to corner him when he gives you the cold shoulder, because, guess what, OF COURSE it's awkward to be in that kind of situation, liking someone and seeing them draw the "clear" limit they don't want you to cross.
It's almost clear for me that Yoon will end up with the boss, because that's how this works: the "new and rich" always wins the "old and average". But, if this was anywhere close to reality, he would dump them both, and be awarded by the Korean government for his service to democracy and free press.