So the reason Alex is a shithead is because he got burned by another shithead? Hmm sounds ...

Or kinda realistic...that happens in real life

It's not an excuse, it's an understanding as to why he behaves the way currently, as exhibits such coping mechanisms. His "BJ Alex' persona might have even have bee a way he tried to distract and reinvent himself, to be able to lie about all of these sexual escapades, presenting a "perfect" image at university, restricting his food and exercising because he has insecurities about his body, having a "flight response" to DG whenever DG started to bring up words like date, having to isolate himself and having panic attacks when he gets memories of his ex..... Considering that the ex appears to have been his first, and only relationship and it carried him through his teenage and early adult years, and ended badly, it did have an impact on him, even now. Guessing the plot might end up with DG being the "fixer" or the "saviour"...

I also have a feeling that the guy he used to like either ridiculed him for being gay or cheated on him which is why he has a history of behaving intense jealous behavior when he thought DG might be taken away by BJ MD. It doesn't excuse his actions but gives insight on why he is the way he is an his insecurities and the birth of his BJ alter ego

Hopefully the background as to why he started camming and creating this false image of himself will be explored in the next few chapters, maybe the morning after when he's hungover and feeling a bit exposed it will all come out. The question is then, will DG accept this real Jiwon seeing as he isn't his idolised Alex or sunbae.

And the plot thickens.
You bring up a good point. At this time DG is “in love” with his idol, not the real person behind Alex. He might be developing feelings for Jiwon, but everything is based on what he’s seen from Jiwon/Alex until this point. If Jiwon suddenly softens up, realistically speaking, DG might not be interested in a softer Jiwon. Of course more likely than not they are the end game, so this shouldn’t be a major issue, but it would be interesting to see DG struggling to feel the sabe intense feelings for a nicer/ softer Jiwon and build from there

Exactly