I just think you need to read it again because the story is clear on why about your question
^agree with this one, i think his motives/reasons for choosing so were p clearly explained.
He used the older brother to get close to the younger brother. Simple
Yes if I let it go and accept it I get it but on a base level I'm getting confused cuz there were other ways of meeting him.
Pray tell in what ways you think so that might make the story much more interesting because I'm assuming the "ways" you think about are the sane versions (like simply just coming up and introducing himself as "hey I was the guy you met when you were a kid, all bruised and shit) and that would in turn just be normal and far from how Won would usually think given his circumstances and views in life. He was abused and despite his well educated demeanor before he showed his true self to Jinha, Won is mostly convinced that the only way he can be closer to Jinha is to make Jinha obsessed with him just like how his late exes were.
I understand and can see the character logic in everything that happened so far. By character logic, I mean I see why that character did that for what that characters motives and personality is. Except why would won go for the older one if he wanted jisu. I am stick stuck in confusion. Although I do accept that won would not be free from the tutor if not for jisoe (I spelled his name wrong the older one)