I know this piece by heart and has so for many many years. I am a lousy score reader but thankfully can memorize music rather easy. As you have read Chang's book, I believe I can refer to his division between different types of memory technique? Muscle memory, keyboard memory, music memory, theory memory and sight memory. My strong areas are muscle memory and theory memory. What you need to do is understand what you are good at and use your abilities. It is not for certain that my method would apply to you
But my story is that I mainly see that it is an A-B-A nocturne, that we have a very repetitive left hand in the A-part, a rather equal right hand melody in the A-part, a more variated left hand in the B-part while the right hand is a rather easy octave playing with right hand. The difficult parts are of course the rhythmically difficult passages as 11 over 6, 22 over 6 etc.
After seeing this, I make sure I learn the A-part's left hand so I can play it in my sleep so I never need to think of it. So to speak, force into muscle memory. This takes quite some times and at least a couple of 1000 repeats. But it is only a couple of seconds long so it did not take very long. Then I learn the difficult parts the same way, just force them into memory playing both hands. It will take at least a month or perhaps several before you can do this in your sleep. Don't practice it more than 30 minutes per day. It is better to sleep between the sessions. When this is learnt, you have completed 80% of the piece and from here, I just playing the rest right through until I got it right. I removed the sheets as soon as possible and just had them turned around on the grand and checked only if needed. I rather guess and use my musical memory than turning the sheet around and check (that is what the lazy man does).
From the first time I succeeded to play it all through from memory until I knew that I was always able to play it from memory (performance level) took about another month. The entire process took about 3 months.
Perhaps a thing or two here can help you. Good luck!