4. I think it is an appropriate metaphor. Brain has the faculty of talking, laughing, crying, thinking and so forth. Without brain, human cannot exist. In the similar way, engine performs all the functions in the vehicle. The car is consisted of more than 20,000 parts. Even though it is not small number, it is nothing when it compared to the human neuron system. Anyway, neuron system is controlled by brain, of course, car parts are controlled by engine. Therefore, when there is a little bit damage at any part of the brain, specific features cannot be operated. It is the same story about the vehicle.
5. There are four evidences. First, if placing an object in the sprit brain patient's hand, left-right asymmetry observed. Second, when showing an image in the sprit brain patient's visual field, the asymmetry is observed. Third, dichotic listening test shows language is lateralized. Left hemisphere is superior for linguistic stimuli such as syllable however right hemisphere is superior for nonverbal stimuli such as environmental sounds. Finally, the corpus callosum makes the two halves become two different mental spheres.
6. The answer is NO. The evidence is provided by the patterns of neuronal activity in people reading different kinds of writing. For instance, Japanese language has two systems of writing. One is kana which is based on the sound system of the language. The other system, kanji, is not based on that system. Japanese with left hemisphere damage are impaired in their ability to read kana, while people with right hemisphere damage are impaired in their ability to read kanji. Plus, experiments suggest that the right hemisphere is better and faster than the left hemisphere at reading kanji, and vice versa.