If this is state employment, which is what it strongly sounds like, you are fighting a terrifically impossible battle to get anything much changed. The departmental HR is in complete control of the top tier execs, and they have some leeway to create and change positions, but you know what? Unless you are terrifically politically connected at the state level, they won't. Your department will have an EEOC person, and there is always the overall state EEOC office, but you're pitching the job as a "different compensation for gender related reasons" and that dog won't hunt. This is just a trap that you've fallen into with this particular position, in this particular department. You're doing a lot more than the traditional assistant, you know it and they know it, and the only way to get a raise in salary is to change jobs, change titles, ergo change pay grades. They can overcome handily by showing that yes, sure, they'd hire a qualified person of the opposite sex for a similar position anytime.