Unfortunately you will not be able to unlock Scholar (SCH) before finishing Sastasha.

One of the requirements to unlock SCH is to finish the "Sylph-management" Main Story Quest.
This quest will be unlocked along the story after you finish the Sastasha, Tam-Tara, and Copperbell Mine Dungeons, and The Bowl of Embers (Ifrit).

My best suggestion is for you to be a member of Free Company and ask for internal help from fellow players. I believe the community is there to help you out.