I think that the applicant should consult a plaintiff-side employment lawyer.

The manager's actions are highly problematic, both in terms of suggesting that sexual favors might help the applicant get the job (or that refusal might result in the loss of the job), and in terms of what might happen if the applicant gets a job offer and takes the job.

A lawyer can help advise the applicant about how to proceed during the application process, and about what to do and how to protect himself if he gets a job offer.

The lawyer would ordinarily work on a contingency fee basis, meaning that if a legal claim is made or litigation results the lawyer gets a percentage of the recovery, but that there is no fee for providing counsel about a strategy.