I don't know of any good resources, but application of the laws is mostly common-sense, with a slight bias towards non-discrimination in the gray areas.
It doesn't take a lawyer to tell that Hooters' primary product isn't chicken wings (Chris Rock even made a joke about it).
The reason behind the laws isn't common-sense, in the case that the 1964 Civil Rights Act is basically a list of "things currently happening that we think are bad" rather than an exhaustive list of things it's bad to discriminate on; it's also limited somewhat by the legal framework that the US congress was working within.
Labour laws in the US are also weird for similar reasons. There was a point at which union members were beaten and killed, with the local police being bought-off to not intervene. It escalated to at least one pitched battle between a private army and workers. Things like assault, battery, and murder are enforced at the local ("state" in the US terminology, not in the meaning everywhere else in the world) level not federal level, so rather than arresting the people doing this, laws were passed giving special protections to unions. Then a few decades later people argued that the special protections made unions too powerful and a bunch of extra rules limiting what unions can do were passed.
