1. Should the underlined verb be in the past tense or should it be in the present perfect tense? -- This depends on whether she is still teaching young children and adults.
After coming to Japan, she taught young children and adults at ...
She is currently teaching at ...
2. When you are referring to a specific person in a book, do you use the past tense or the present tense? -- Again, it depends on context. Usually, I would use the present ('what is'), but if you're discussing a book that the listener has finished reading and laid aside, you might use the past tense.
In "Gone with the Wind", what was the main male character's last name?