Guilt
Booth is a very guilty man. His life after marrying Amelia is one long train of offenses. First he cheats on her while in prison. Then, when he gets out, he repeatedly resorts to compulsive gambling. He wastes their money, accruing ridiculous debts, which they could never repay. Over and over he medicates his feelings of guilt by gambling. Eventually, he sees that he has to man up and make things right with Amelia before he will feel any better. When they receive Amelia's mom's inheritance, he finally has been given the chance he needs to change his behavior going forward from a solid starting point.
Debt
Booth is not good with money. His gambling debts are not the only example of debt in his marriage. After he cheats on Amelia with Miss Matthews, he owes her for his infidelity. His life after prison becomes one long endeavor to repay Amelia for his unfaithfulness and to rebuild trust with her. In the end, Amelia's mom is the savior. Her death and subsequent inheritance provides an opportunity for the couple to once and for all rise above their collective debts. The irony here is that her mom never wanted Amelia to marry Booth, but her provision is what ends up saving him too.
Temptation
While Booth is wrongfully imprisoned, both he and Amelia are tempted to infidelity. Miss Matthews visits and seduces Booth while he's in jail. Unfortunately for Amelia, he doesn't resist her charms. On the other hand, Amelia rejects all of the advances made to her by various men in her husband's absence. She loves him and remains true to him always. This temptation which they both undergo serves to illustrate the role each of them plays in the marriage. Amelia definitely survives as the better man, so to speak.
Money
Finances play an important role in Amelia and Booth's marriage. Since he is impulsive, he tends to blow through their money in irresponsible ways. For example, he gambles when he gets out of prison. Eventually, this bad habit lands him in a debtor's prison. After this, Amelia is the one who gets them out of debt through her careful money management. Finally, her mom's death is their saving grace as Amelia inherits her mother's estate. Her faithful stewardship of their finances is what really inspires Booth to change his habits and appreciate her hard work.
