They didn't check the rope before if it can be used regularly, it might snap after few of them climb on it.
Best way to escape as a whole group is restrain or kill Isabella, that way she wouldn't sound the alarm or go after them.
2015 might be the last book that would be published on paper, society might switch to digital only so the current date and world beyond could be totally different.
Maybe the demons occupied only part of the world, but might as well rule it as a whole, something like WWII Axis Powers but also if they won, so there will or never have a place to stay.