For the studies/etudes requirement, I would recommend you get Czerny - The School of Velocity op 299. It's foundational technique for the serious pianist. These are etudes, not exercises (like Hanon). Start with the first few. The point is to play them with clarity, precision, musical line, dynamics while you try to reach the tempo indicated.
I recommend you continue with Bach preludes and fugues for your polyphonic piece - how about the pair in A major from Book I, the prelude is very contrapuntal (as is the fugue, of course).
I agree with your teacher to continue working on the Tempest sonata, then you can perform the whole thing.
The piece you want should really be something you've heard that you like and which is within your reach. What composers do you like? Grieg is enjoyable, but gets boring quickly, imo - better for sight reading at home, rather than preparing for a recital. I recommend you explore Debussy - it's a unique approach to music and a very important composer for pianists.
Just curious, why are you pursuing a MM at 33? How do you support yourself?