Responses
He's not "disgusted by Bum though" and he does "like" him. No they aren't affectionate, they are two men who are in a codependent relationship and have their own mental health struggles which influence current behaviour such as Sangwoo having trauma about his mum, presumably his reaction over not being able to give head was linked to this, as his reaction of dwelling on this for hours? afterwards then having to go away from the scene and tell him self he is okay after, isn't behaviour you would expect from someone that is just trying to act like a prick to their partner.
It's confusing if you're not borderline psychotic.. he vomited cuz he was disgusted with doing it with Bum? is that it? But he needs to keep up the pretense so Bum would follow him thinking he at least likes Bum too..? That's how I see it.