I know it was so creepy but I think he loved SW deeply even his love was twisted

It was actually very understandable, he said so in the 2nd r 3rd episode, that he loved both of them dearly, Da Kyung and Sun Woo, and it made it hard for him to decide what to do. I detested his character for being such an immoral acting person throughout the show, and not because he loved two woman at the same time, I think one's feelings aren't something to control, they are byproducts of one's action and one just need to take care of his doings, not their feelings (which can be very twisted, just like how Tae Oh felt) so everything can finally get straightened.

Even tho we got alot of background if i remember correctly we never got flashbacks of the male lead like other than his mother and the fact theres a high chance his father cheated on his mother ...he obviously had some mental issues (we all do)