In stage 1 of Kohlberg's Theory of Moral Development, individuals understand that rules are set and they must follow them or they get punished. They also come to understand that one must do what they need to do to get the results they want or need. In David's case, he knew he must follow the rules in order not to get punished, but it seems that either way David was punished. He learned that basically no matter what he did, the result would end in punishment. He continued to try to please his mother to get what he wanted or deserved but that never seemed to happen. Kohlberg uses the "Heinz Dilemma" when explaining his theory. David didn't always make the moral choice. He stole from other kids, stores, and so on, but he did so to survive, which is directly related to the Heinz Dilemma.
Stage 2 of Kohlberg's Theory of Moral Development is focused on "interpersonal relationships" and "maintaining social order." David continued to try to be somewhat normal and fit in with the other children as well as in society by getting a job and trying to do well in school. However, he still wasn't getting the response he wanted from his mother. She continued to punish him, especially when he didn't bring home enough earnings.
The Post-conventional Stage is Kohlberg's final stage. It is focused on the individual actually seeing themselves and others with differing views and opinions. By this point, the individual can follow their "internalized principles" to determine what is right or wrong and how they are going to react. When David grew up and was on his own, he chose not to fixate on the past. He chose the moral "high road" and focused on bettering his life with his new family.