In Chapter 27, there is further characterization of Bob Ewell that depicts him as the reprehensible man that he is.
- Bob Ewell becomes the only man Scout has ever known of who has been fired from a Public Works job created during the Depression because he was too lazy to work. However, Ewell mutters at the welfare office that those who run Maycomb would not "permit an honest man to make a living." He even makes innuendos that Atticus "got his job."
- Bob Ewell is suspected of trespassing upon Judge Taylor's property. One Sunday night Judge Taylor went to the back porch to let his dog out and discovered that the screen door was swinging open. After seeing this, the judge sat the rest of the night with a shotgun across his lap.
- After poor Tom Robinson dies, Mr. Deas created a job for Helen Robinson. However, when Helen walked down the public road to this job, Bob Ewell "chunked at her." Afterwards, Mr. Deas walked Helen home past the Ewells. Outside the Ewells' place, Mr. Deas called out to Bob and threatened to have him put in jail if he threatened Helen again. When Helen walked to work the next day, Bob Ewell followed her, then leaned on Mr. Deas's fence outside the house until Mr. Deas came from his store and threatened Ewell with arrest again.
From these three incidents, it becomes obvious that Bob Ewell feels no guilt for being the cause of Tom Robinson's death, nor does he feel anything but hatred and envy for decent people. Because he is shiftless, envious, and vengeful, Bob Ewell retaliates against Atticus for what he thinks are Mr. Finch's humiliations of him. He harasses Helen Robinson for reminding him of what he has cost Tom Robinson, and he antagonizes Mr. Deas for defending Tom Robinson.
The three incidents to which you refer are: 1) Bob Ewell gets and loses a job because of his own nature and his ways but he blames his losing it on Atticus; 2) someone attempts to break into the house of the judge who presided over the court case, Judge Taylor (it's an obvious assumption that the person who attempted the break-in was Bob Ewell); 3) the Ewells throw stones at Helen Robinson when she walks by the Ewell house on her way to and from work at Link Deas which causes Deas to warn the Ewells to stop. These events tell us what a petty, immature, vindictive, and dumb bully Bob Ewell is. He was made to look foolish and he was shown for the lazy, abusive alcoholic that he is. He did the things he did - blame Atticus, attempt the break-in, and harass Helen Robinson - as his way of getting back at and scaring those he feels wronged him.