Yeah, so no updates so far. I know it's killing me, too. I literally check the website every day and the "in preparation" notification is making me go insane with how much they're milking this story.
yes, jingi and heongjae are full-blooded brothers. The door is symbolizing c/sa.
the man jingi is living with is his uncle, who is the reason why he's in prison.
It's literally the same penthouse that Jaekyung from Jinx lives in.
Don't believe everything Hollywood shows you. The anatomy of the human head is a complex thing that can miraculous survive stuff if you're lucky enough. Many people who shot themselves in the head have gone on and survived with some form of disability afterwards.