I just took 46 this morning. Yeah, the 4th RC passage was pretty abstract and unclear. When I read it I just kept in mind the following: The examples the author is giving serve to illustrate his point that some laws INDIRECTLY or NOT OSTENSIBLY prevent harm, whereas others -- like those that outlaw murder and abuse -- DIRECTLY prevent harm. Thus, some laws that don't seem to cause harm -- the indirect ones -- are still justified, despite the fact that people don't always realize their function.
Anyways, sounds like you still did pretty well on the thing as a whole.