Yess the arm scratching makes me worried as well! I was thinking that maybe it's a sort of self-harm, but he always does it either way so I don't think so. Maybe he has some scars? I don't know, but there HAS to be some meaning (probably a depressing one) if the author is choosing to show it this much ╥﹏╥
As for the asshole, I'm betting a pizza that he's going to see them caring for each other, or even sharing their first kiss or something, get jealous and do SOMETHING to Baekhee either in a way to be seen by Ilwoo or directly in front of him to assert dominance. I have read enough BLs with toxic second leads to see where this is going and I don't think I'm ready...

I hate this one guy who always play with MC , I'm afraid of what he will be doing to them now
And I really want to know already why ML always scratching his arm