What is the ruling on a private driver working for a family where the employer's wife or daughter rides with him alone, knowing that the daughter does not adhere to the legal hijab and he stays out with her late at night, taking her to places of intermingling? Is he sinful if he leaves the job without finding an alternative? And does his fear for his livelihood contradict reliance on Allah (tawakkul)?

It is forbidden for a driver to be alone with a foreign woman in a car because it constitutes unlawful seclusion (khalwa (definition)). However, this does not forbid the driver's work or the money he earns from it. If the purpose of going to certain places is unlawful, then transportation is not permissible due to its being an assistance to sin. But if the purpose is permissible, then transportation is permissible. If you fear temptation for yourself or falling into something forbidden, then it is obligatory for you to leave this job. If you are confident that you will not succumb to temptation, then seek another job that is free from Sharia (definition) prohibitions or has fewer of them. If you cannot find another job that suffices you, then do not leave your current job, and be diligent in staying away from Sharia prohibitions as much as you can.