Hey great, Post. However, I do not think that you can compare the economic methodical expression of ceteris paribus with real life. Economists state ceteris paribus because they know the real world is too complex to be modelled. A model exists because we want to simplify real world conditions. When you write "We want these factors to be constant." it is correct but for other reasons than being close to real life. I do believe, as you say, that nothing will be constant in our lives except of physics.