The class of workers where Johnson place writers of dictionaries is those "who toil at the lower employments of life." This refers to the people with low paying jobs. These people have fears, knowing that they are going to be punished if they don't succeed.
Yes.
Think of a thesis statement as something that you know or believe is true. For instance: "The dog is brown." After you have told this to someone who is blind, you would go on to explain how and why the dog is brown. The thesis is the main topic in a story. After the thesis is stated, you would go on to explain how and why the dog is brown.