My own theories are monoe and poniko are related to incidents too, like how monoko is killed in car crash theory.
Monoe was kidnapped by the guy outside of the cave (kinda like a dark alley way/ tunnel). The last mado seen of her is either in the tunnel or on a newpaper (hence the forced smile)
Poniko is most likely to relate toward assault hence the groping imagery in uboa world (Idk if thats popular theory). But i think the reason she does it because she was trapped in the room (hence why you cant open the door during uboa event). She was losing her senses and assaulted mado, the bloody puking monster in uboa's world is just a crude memory of what mado seen in the dark. Poniko was coughing blood probably due to sickness or fatique
Madotsuki has a sensory processing disorder that cripples her ability to live comfortably. Certain sights, colors, sensations and smells are too much for her, so she avoids going out unless she has to.
Her dreams are her favorite escape, because she can experience anything and everything without being overwhelmed. They do get scary sometimes, though.
The Number World, for example, gives me the impression of negativity. Hideous, clashing colors, random numbers, rooms to make you feel claustrophobic, and faces on walls make it feel like an approximation of a city, neighborhood or apartment complex. The fact that one part leads up a flight of stairs to a door that looks like her bedroom door kind of solidified the idea that the Numbers World is how she might see her surroundings in the "real" world.
Kyukyu-kun could be an example of someone she's become very averse to being around, because they keep engaging in activity that overwhelms her (which could range from putting their hand on the staircase rail, causing squeaky noises, to wild clothing choices, to making too much eye contact with her - whatever it is, it stresses her out). Could be a janitor, a neighbor, really anybody.
I was looking at that picture of Poniko and Mado, and just thought of something else. To get the Uboa event, you have to keep turning off Poniko's lights.
What if Madotsuki and Poniko were friends, but Poniko's room was too overwhelming for Mado when they hung out, so she kept turning off the light? So, Poniko, thinking she could get the best of both worlds (hanging out with her friend without being bothered by there being no light in her room), just…made everything glow in the dark? Covered everything in black light fluid, painted over her wall decorations, window and carpet so there'd be a different image when the lights go off, etc and she thought Madotsuki would find it cool and a nice compromise, but it actually just horrified and triggered her?
Dreams are just a byproduct of the light sleep cycle brain, deprived of input and desperate for stimulation, rewiring conscious experience into a temporary feedback loop on itself to feed that craving. They contain no inherent meanings.
Madotsuki is actually my wife, and the ending was just her jumping into my dream world ( I meet her there everynight ) .