Quote 16
I know that already, everything's breakable. (1.552)
This is a pretty profound line from a five-year-old. Most kids don't learn to take care of their things for a very, very long time. Jack has learned this lesson pretty early.
Quote 17
Alice says she can't explain herself because she's not herself, she knows who she was this morning but she's changed several times since then. (2.116)
Jack is talking about Alice in Wonderland here, and he's relating it to himself. When Jack's view of the world changes because of new knowledge, he changes right along with it. His identity, especially at such a young age, is closely tied together with how he sees the world, and how he thinks he fits in it.
Quote 18
Stories are a different kind of true. (2.271)
Lots of the "stories" Ma tells Jack, like How the Berlin Wall Fell Down and Princess Diana are stories of actual events. Even the fairytales, like the mermaid who has a child in captivity, are allegories. Is there anything allegorical about Room itself?