It is called dentin. It lies beneath the enamel and the cementum, and makes up the majority of the tooth.
Probably kindness and caring about his cousin. This is because someone wouldn't do this unless they really cared and is a kind person.
Probably the elderly- maybe 70+? since they have lived almost all of their lives
Melanocytes produce little Melanin and that is what gives your hair and skin its color.