What three things does Bob Ewell do that alarm Aunt Alexandra?

In Chapter 27, Aunt Alexandra is frustrated that Bob Ewell has once again caused trouble. She believes that Bob seems to have a "permanent running grudge against everybody connected" with the Tom Robinson case.

There are three things that Bob does which alarm her. The first occurs when Bob gets fired from his job at the WPA (Works Progress Administration) due to his laziness. After he loses his job, Bob goes back to collecting welfare checks. As an example of his lack of grace and gratitude, Bob openly complains that he is an "honest man" who has been denied an opportunity to make a living.

Not long after, Bob Ewell takes to stalking Judge Taylor. One Sunday evening, as the judge is reading, a scratching noise is heard from the rear of his house. When Judge Taylor lets his dog out, he discovers that the screen door is open. However, out of the corner of his eye, he manages to catch a glimpse of an intruder skulking away. Later,  Mrs. Taylor comes home from church to find her husband with a shotgun across his lap. The general consensus is that Bob Ewell is the one who's been stalking Judge Taylor.

Not content with the all the trouble he has already caused, Bob Ewell then harasses Tom Robinson's wife, Helen. After the trial, Helen is given a job by Mr. Link Deas. To get to work, however, Helen must go a mile out of her way to avoid the Ewell home. Helen is harassed at least twice by Bob Ewell; it is only when Mr. Link Deas threatens to bring Bob up on charges that he stops harassing Helen.

For his part, Atticus explains that Bob is just trying to salvage his wounded pride. During the trial, Bob imagined that he would be the star of the proceedings. However, his bombastic and rude behavior alienated the jury and courtroom observers, and it left him looking foolish and small-minded. More than anything, Bob knows that very few people really believed his and Mayella's story about Tom Robinson. Atticus tries to reassure Aunt Alexandra that Bob has "had his fling with about everybody now, so he ought to be satisfied. He’ll settle down when the weather changes." However, as we later learn, Bob Ewell's actions are only a precursor to his brutal attack on Scout and Jem after the Halloween pageant.