Both of these questions are important, but they are very different questions.
The narrator's identity is the tougher question. At no point are we told if the narrator is male or female. We're not even told who the narrator is. We know the narrator has extensive and intimate knowledge of Omelas. The narrator seems to have intimate knowledge of both Omelas and our world. When the narrator uses the term "we," he or she seems to be from our society. When he/she discusses what the citizens of Omelas feel or think, the narrator seems to either be from Omelas, or, more likely, to be its creator.
As far as the narrator's feelings toward the tortured child, that's almost as complicated. I'd say the best summary is distant compassion. Look at the actual description of the child, and the level of detail is amazing. It could easily nauseate a reader, or break a heart. At the same time, some of the words are formal ("excrement," rather than something cruder), and the tone is speculative and tentative: the narrator says "perhaps" this happened, and "perhaps" that.
The narrator seems to be at once withholding personal judgment and forcing the reader to make one.