SPOILERS: (don't read if you haven't watched the series yet)
So, I'm writing this as a reply to the very first review. (Bertilla, not to offend you but we can't exactly reply so...)
The answer to all your questions- THAT'S WHY SHOWS HAVE SEAONS.
If they were to explain everything in the first season, there would be no next season. We don't know why they decided for 1 season with 6 episodes, it's probably to see the reaction of the people to the series first and then have a second season if they do.
Now, what we can think of the baby surviving and that the monsters could not really use more of that "light" to burn that fragile body might just be the reason and explanation of the series. A very basic and simple reason would be - sacrifice and love, maybe. The parents tried to protect the baby till the very end which might have made the baby safe because it was a noble sacrifice and for the love for their child.
As for the fact that we already know that humans can be really terrible
and it's nothing new and there are multiple shows about it, it's very true. But through this series we are again reminded of the fact. In all stories, humans can be both terrible and good. It's not just Hellbound which has this concept, most stories do.
The interesting concept of society that I noticed here was how fragile humans can be when they fear the unknown. Or how there are always people who would take advantage of bad situations. Or how something that started as a noble cause (by Jung Jinsu- so people can believe that all this was for the greater good of the world) can turn into a horrible situation.
As for your opinion, I respect it, it might just not have been to your liking but I just sort of wanted to give my opinions on your questions too. Thank you, have a great day!