Unfortunately, the 2nd movement is (still) above my level, and I am not anywhere close to the level of the 3rd.
I have thought about Bach's inventions, but I have always had problem with their polyphonic nature, and I'm afraid I'll just butcher them.
Bach 2 part inventions are great for developing the two track mind. You play the right hand until it is automatic- ie memorized by your inner brain, not involving your cortex or concious thought. You play the left hand the same way. Be sure to learn them so you can play them slowly as well as fast. Make sure each hand is learned with no mistakes. No butchery allowed.
Then you turn the two parts of the brain loose at the same time, that is to say play both hands at once. Slowly with no mistakes. If you make mistakes you are not practicing slowly enough.
I learned Moonlight part 1 age 11, part two age 32 and part three age 55. The movements vary wildly in the difficulty involved.
Graded instruction books with numbers are boring, but do put pieces in the right sequence. I learned from the John W. Schaum ones up to about grade IV. After that the teacher put me in a book of chestnuts, "
everybody's favorite piano pieces for the young student" Amsco music publishing co, nyny, everybody's favorite series book #80. Great resource, probably long out of print. At the charity resale shop five years ago I found another bound book of chestnuts,
Masterpieces of Piano Classics selected by Albert Weir, 1907, pub Carl Fischer NYNY, #03619 There are Lots of fun middle difficulty pieces in there. I'm working on Bizet
Habenera right now.