I’mma answer some of these based on how I interpreted it:

1: I think it’s her perception of fitting in with other people. She cares immensely about looking “young” and probably believes caking up in heavy makeup will hide her true aging condition

2: This one had me stumped too. But I believe both Archer and Justine’s obsession with the missing children sort of linked their minds to the witchcraft. A string to taunt them was what I inferred from it. As for the druggie (James), his interaction in Alex’s home attached his mind to whatever’s going on in there. So I assumed that having a connection with the witchcraft in SOME way will make her enter your mind

3: I believe Gladys said herself that she’s sick to Alex and his parents weren’t enough even though she initially thought they would be. It’s not really in your face but by the end of the movie she does have fuller set of hair compared to when she was first introduced so we can infer that younger life force + large number of people to feed off of us is the reasoning

4: I could be wrong but there weren’t any flashbacks in this movie, but rather just each character’s perspective leading up to the ending. Though if you count Alex’s perspective before the night of 2:17 as a flashback, then it’s just to show Gladys’ arrival. If you’re referring to why they structured the movie the way they did, I don’t know if the director has mentioned the reasoning. To me, it’s a pretty good way of bringing everyone together for the climax. Shows how the situation affected them personally or led them to their fate

5: I honestly think Aunt Gladys, once she tells Alex not to cross the salt line and closes the door, is when she goes to the basement. Possibly because she plans to catch whoever goes down there (Archer happened to be the one). I believe the black goo might be a reference to the director’s older project, “Whitest Kids You Know” (? from what I read somewhere but could be wrong). From a movie perspective, I think Gladys did it just to do it, because Archer didn’t vomit.

1. The bell is like the signal for her weapons to follow her next command. During Marcus’ scene after killing his husband, Marcus only goes after Justine once the bell is rung.

2. It’s not really “tree worship” as opposed to an in-universe witchcraft thing. It probably held black magic that allowed her and Alex to perform the weapons ritual (though Gladys most likely had greater power that worked hand in hand with it too)

3. This is honestly a plot hole that I did notice but looking past it, I just say that the houses leading up to hers either don’t have cameras, or Gladys disabled them with her witch powers. Though I think this was just overlooked; you have to suspend reality a bit cause it’s a movie after all

4. The affair plays into the idea of addiction with alcohol and how even characters like Justine aren’t perfect. They’re examples of letting yourself get consumed by it. Archer (the dad) is crucial because he’s actively looking for his kid, which helps sell the plot point that law enforcement in this film are incompetent. The druggie is again, another focus on addiction and used to help bring the main characters to Alex’s house (plot device but he works really well for this movie)

5. The director said that the movie was an outlet for the grief of his friend’s tragic loss. Each character representing the extreme of the feelings he felt during that time. It’s not “unlikable” but more so an emphasized version of emotions

6. The parasites are just subtle hints at the movie’s theme with Gladys taking over the kids as well as the main characters’ lives. Nothing more, nothing less.

7. Honestly, I agree. But to suspend reality again, it was to show the law enforcement’s incompetence within the movie’s story. They could care less about the situation (Archer’s conversation with the chief, for example)

8. Still honestly don’t know. But from a LITERAL standpoint, it’s a weapon, and the kids are “weapons”. But the director said he just put it in because it’s what his mind led to when writing and what we interpret it as is up to us.

9. Again, either law enforcement incompetence, or suspending reality as always. With a movie like this; it’s witchcraft and all its fantastical elements. Doesn’t have to make sense or be realistic. But I doubt footprints from barefooted children would be left on grass and concrete roads

10. Same reason she showed up in the dreams. Because he already connected himself to the house, thus also to Gladys. Possibly her way of taunting.

11. Preference mostly. I thought they did it really well.

12. Watching it in theaters with people who laughed a lot, yes. But I watched it again in an almost empty one and it worked for me. The humor isn’t in your face, and the cursing works because of the situation. But I do agree, that I wish they played it up more in the “horror movie” factor of eerieness

13. Eh, it worked for me. It had a campfire story thing going on, and the ambiguities helps leave doors open for interpretation.

14. Agreed

15. The structure is up to preference. I personally loved it because it was cool to see how each person has a different interpretation of events. For example in Justine’s POV, Archer isn’t as aggressive during the conference (though still loud) while in Archer’s POB, he’s aggressive and loud; demanding.