The doctor didn't give the kid meds, the medication is reserved solely for "the hounds" when they need it. Which is why the situation is so messed up, and why he stole.
I don't think he was abusive either, Woojun was shown to be sick often since he was first introduced. And the dad seemed genuinely happy/emotional when receiving Woojuns drawings from Teach :(
This is what I meant when about the author probably gonna pull a plot twist on the story in the future chapters.
I'm just saying this because based on my reading experience, in apocalyptic stories like these ones some of the nice looking people that look kind and caring usually end up being devious. But that's just a theory.....a game theory (人 •ᴗ•)
Right?? And thank you for pointing out the open door policy because that completely slipped my mind. \(°o°)/ !!!
After reading ch 19 it made think... what if the reason he didn't want the teacher to enter was because he didn't hide the medicine yet? But that's just silly bc medicine, like pills, usually comes in those pads or small bottles and those are easy to hide, same with syrups (usually in small or medium sized bottles and very easy to hide).
The dad could have just walked in first and hid the medicine in his pockets or under the pillow or sumn, brought the teacher to the kids' room, and then continued on with his day.
Like I feel bad for his bloody ending but the way he acted just sent alarm bells in my head.
(• ▽ •;)

That was one way to set up a story add to the plot, like woah.
Also, like, I feel bad and don't condone the way that he had to die in the name of giving medicine for his son but a part of me is suspicious, like in chap 15 he said the doctor already checked his boy out so wouldn't that also mean giving the kid some medicine? Like why would he need to steal some more if the doctor gave him a visit.
And the way he was blocking the door from letting Guwon see the kid. Like what if the dad wasn't scoring the drugs for his son but for himself y'know? Maybe he's selling it to outsiders or using it himself. I mean it's still 19 chapters in so it's still to early to tell...
Yeah, sorry about the ramble, but I've read way too many books and comics with similar tropes and when a plot point like this comes up it's usually a way for the author to pull the rug under the reader and go "oh yeah, plot twist, he did deserved that death because he was *flips notebook* he was using the drugs for himself and was actually abusive to the kid, that's why he was always sick" or something like that.
Still, I feel very shocked that he to go that way, they could have made him a scavenger or put him on permanent guard duty outside the gates but nah it was 39>1 vote to die or not die. Very mediaeval style of execution, makes me wonder which stories the author took her inspiration from to make this.