They can but it's like a drug. Aline doesn't want to get out, which is a huge problem and it eventually would kill her and she can't be forced out in the real world. It's like Matrix rules. I don't get your hangup on the painted world.
Maelle showed up when real life Alicia went into the painting. It took "60 years" because time operates differently from the real world vs the painted world.
Clea DOES care about the battle, she wants it to end so Aline is forced out of the painting so they can focus on the war with the writers to get real world revenge for Verso.
We can assume methods of art have powers in this world. Painters, writers etc etc and for some reason the writers are assholes and started the fire for unknown reasons.
Yes, Sciel had a husband and child. Lune had a tough upbringing and had OCD. What's the issue? That's part of the story is whether or not you consider the painted world real or not.
Kinda sorta. The people of Lumieire didn't know what it was but it was to let them know they should enjoy their remaining time together. I don't know what you're talking about with expedition 32.
It's kind of weird you hate the story for being all "fake world" but then you like Maelles ending more which is justifying the existence of the fake world lol