I'm not sure if I can answer the first question, but I think areas Feng Shui principles are descriptive, kind of like the law of gravity. Even though you don't believe in the law of gravity, it will still affect you.
In level one SFQ, Master Lin gave an example of a family he visited once. He noticed something in the basement and said that people in that house suffer from a particular ailment; I think it was back pain or something like that. It turns out that it was true. Once they fixed the problem, their health problems went away.