Is it unlawful to work in a job that was obtained through nepotism, but is nevertheless commensurate with my qualifications and experience, and must I leave it if that is the case?

The ruling on remaining in the aforementioned job depends on the extent to which it is performed as required. If you are good at performing it and do it as required, then there is no harm in you remaining in it. However, if you are not good at it and cannot perform it as required, then it is not permissible for you to remain in it, even if your parents order you to continue. This is because there is no obedience to a creature in disobedience to the Creator. Your remaining in a job that you cannot perform is a betrayal of trust and an unlawful consumption of public funds.