He learned since he was little how abbandonment feels, because of this he acted in the worse way he could've: keeping Minho with force, leaving him no way to escape.
It's wrong to say that he's not a caring person cause he actually wants to prove minho that he loves him and tries to be a better person : "I'll let him work as much as he wants. I'll suppost him and cheer him on, whatever he wants to do. I'll support him as much as I can..."
Lastly for all of those that say that there hasn't been any progress in the story or character developement, they haven't read the story in the right way. Cause there for sure is developement and noticeable changes in both characters especially Wookyung. Just try to think about it: at the beginning of the story he wouldn't even think of taking Minho out and didn't give a fu** of whatever he did or if he hurt himself, he just had to stay with him...recently thought he did take him out (twice) and started noticing how depressed he was and his heavy drinking. He definitely started being more careful and caring, and of course his feelings are continuously kept growing. If you go to the first s** scenes you can see that he only puts on a satisfactory-psycho kind of face, while in chap 22-23 you can see that his gaze is completely changed and his touch (yes it's still sort of aggressive at times) but it's way different from before. He is much worried now about Minho's wellbeing, even if it's not in the right way (he gives him joints instead of alcohol)...