>>the first cause which began the cascade is unobservable<<

Saying it's unobserved is just a veil we throw over it so as not to notice the imperfections. Is it a first cause or not? If it is, then it violates causation as we know it. If it is not, then god is not the beginning of everything since the whole point of postulating a first cause is to avoid that pitfall of an endless chain of causation--of something preceding god.