Reddit mentions of Mastering Piano Technique: A Guide for Students, Teachers and Performers (Amadeus)

In addition to a teacher, there are:

• Mastering Piano Technique by Seymour Fink (video.) A good resource of various movements we can do to achieve our musical goals.
  
• What Every Pianist Needs to Know About the Body by Thomas Mark. Helps to update the conception of your whole body, not just the fingers, hands and wrists.
  
• The Craft of Piano Playing by Alan Fraser. Start with the section on Natural Hand shape first.
  
  Other technique books I haven't read or had a glance at:
  
  
• On Piano Playing by Gyorgy Sandor.
  
• Abby Whiteside on Piano Playing.
  
• The Art of Piano Playing by Heinrich Neuhaus.
  
• Chopin: Pianist and Teacher: As Seen by His Pupils. An insight to how Chopin taught.
  
• Twenty Lessons in Keyboard Choreography by Seymour Bernstein.
  
• The Physiological Mechanics of Piano Technique by Otto Ortmann.
  
• The Visible and Invisible In Pianoforte Technique by Tobias Matthay.
  
• The Art of Piano Playing by George Kochevitsky.
  
  Your mileage may vary. These books I haven't read are often very expensive or out of print, so you may need to go to a library.

Hmm, there isn't a simple answer to that. For theory, the idea of "level 5" is arbitrary, because I don't know what system you are using. PM me and I can ask you a few questions to give you a better sense of where you are with theory, but basically if you are getting into theory that is so advanced that you never are able to apply it and look for it in your rep, then you can probably rest easy, but there's no harm in continuing to learn more.

With technique, it's not WHAT you practice, it's HOW (which is why "teacher" is really the only correct answer here). Technique is primarily for learning the shapes and gestures that you'll find in rep, and secondarily for learning the notes of scales, chords, cadences, etc. Example: you can play a C Major scale with all the right notes and fingers, but you should be feeling for a loose arm so that the weight of your arm transfers from one finger to the other within a hand position, using a circular gesture that comes from the upper arm in order to do so seamlessly and with good legato, and working on shifts of your position that minimize the thumb "crossing under" or 3 "crossing over." For block chords and inversions, you should focus on dropping from above with loose hands (don't prepare your shape on the surface of the keys or even in the air) and letting go from the shoulder so that all that weight goes into the drop. Russian Broken chords and chromatic scales can train rotation, arpeggios are a combination of a few different gestures.

Again, much of this is best with a teacher who knows what they are doing technically (which is not all of them), but you can teach yourself a bit with either of the Books below. The Peskanov books also have a great layout and variety of exercises in them, but ignore his instructions printed in the books for the most part. Start with Piano Olympics level 1 or 2. Always stay loose, use your weight, not your fingers.

A few resources:
-Mastering Piano Technique, by Seymour Fink
-20 Lessons in Keyboard Choreography, by Seymour Bernstein
-Piano Olympics, by Peskanov and then later The Russian Technical Regimen

Wondered what anybody thought about any of these technique books. Or something else you love?

https://www.amazon.com/What-Every-Pianist-Needs-About/dp/1579992064

https://www.amazon.com/Fundamentals-Piano-Technique-Russian-McKeever/dp/1495073017

https://www.amazon.com/Art-Piano-Fingering-Traditional-Innovative/dp/1479285277

https://www.amazon.com/Mastering-Piano-Technique-Students-Performers/dp/0931340462

"Mastering Piano Technique: A Guide for Students, Teachers and Performers" by Seymour Fink, gives great advice and tips on technique. Here is a link to check it out: http://www.amazon.com/Mastering-Piano-Technique-Students-Performers/dp/0931340462