I think you're asking a lot of questions to things that just haven't been point blank answered yet. But if you want my guess to your questions, he either is bleeding because of stress like you mentioned or possibly it might be something related to his accident that occurred in the real world and potentially things are getting worse now, just like his legs are hurting now. I also speculate the sunbae he knew in school in his real life is the same guy in the novel, they both have the same ear piercings if you look at chapters for both guys. I am not sure if the brother is supposed to be like his sister and I believe due to him trying so hard to stay on track with the story that itself has clouded his judgement and decisions.

Reading this feels like it's all over the place. I'm about to drop this..can someone explain it to me? Maybe I could understand it more and I'll able to read it. Why does he keep bleeding when he gets stressed out? Is this an after effect of possessing a character in the novel? Is the boyfriend the friend he has in real life? Is his younger brother his sister? Is his prejudice against the novel characters clouding his judgement and decisions? Why do I feel like he disregarded his brothers statement when he said the title of the novel( lis it because he forget about it?) I wish he could've treated his brother better tho. I understand that he feels like the treatment his brother towards him seems like fake because he's not the og"seongwon".
I'm confused with his interaction with his boyfriend.
I feel like he's being dependent towards him but at the same time using him.