What do the final words of The Glass Menagerie mean? What do the lit candles represent? Why does Tom say the world is "lit by lightning"?
Since eNotes policy allows for one question per post, I will answer your first question.
In the final moments of The Glass Menagerie, Tom leaves his mother, Amanda, and his sister, Laura, for a new life. The catalyst for his departure is Amanda's incessant criticism of his (supposed) selfishness. In truth, Tom feels unappreciated and unloved. He works hard to support his little family, but his efforts often go unrecognized by Amanda. Tom yearns for a measure of independence and harbors a sense of hopelessness regarding his life.
The atmosphere at home is made extremely difficult by Amanda's domineering nature. She nags Tom about his smoking habits and at one stage, even confiscates a D.H. Lawrence book that Tom is reading. For his part, Tom feels smothered by his mother's patronizing and judgmental attitudes; he works long hours at a dead-end factory job to support all of them and yet, she still excoriates him for being selfish and irresponsible. Tom points out that, if "self" was the most important thing to him, he would have left a long time ago (just like his father did).
Because of Amanda's behavior, Tom ends up leaving at the end. After a failed, last-ditch attempt to please Amanda, Tom decides he's had enough. His departure is precipitated by Jim's visit. When Tom invites one of the only gentleman callers Laura will likely get in her lifetime into the home, he thinks he has finally done something right. During the visit, however, the ladies discover that the gentleman caller, Jim, is engaged to be married to a woman named Betty. After Jim leaves, Amanda turns her fury upon Tom, accusing him of making fools out of her and Laura.
Meanwhile, Tom had no inkling that Jim was engaged, and he is blindsided by Amanda's unreasonable anger. This time, Tom leaves for good. At the end of his monologue, he begs Laura to blow out her candles; he can no longer bear the sweet memories of his sister. They imbue him with guilt and pain. Laura's lit candles represent an innocence that can be easily manipulated. Amanda smothers her daughter's spirit by holding her hostage in an oppressive fantasy world of embellished manners and faux elegance. Basically, Amanda represents a stifling influence in Laura's life. The candles also represent Laura's hopes, ones which are extinguished when she discovers that Jim is engaged to Betty:
The holy candles in the altar of Laura's face have been snuffed out. There is a look of almost infinite desolation.
As for Tom, he no longer wants to live where lit candles can be snuffed out. He wants to go where he can decide who he is and what he wants out of life; in short, he seeks a world "lit by lightning." Unlike the light from a candle (which can be snuffed out by human breath), no human being can control lightning, a natural phenomenon. Lightning is invariably dangerous as well as exciting. It has a power all its own. So, to Tom, a world that is "lit by lightning" is an exciting world filled with possibilities. In a world beyond Amanda's control, Tom believes he will thrive on his own terms.