Tone simply refers to how the author feels towards the subject, or towards something. You will know what the author's tone is implying by the words he uses. While 'mood', refers to the feeling of the atmosphere the author is describing. It is what the author makes you feel when you read ther writings.
a feeling of being sorry for doing something bad or wrong in the past : a feeling of guilt I could forgive him for what he did if he showed some remorse.