Wow, thanks to all for listening and commenting!

@ dreamer 66: Now I'm not sure whether you *think* it's a matter of stretching or not?
I think it's a matter of streching from one note to the next, but not from the bottom (thumb) note through the whole chord. It has helped me a lot to practice it slowly and legato, keep the fingers as close as possible to the keys and keep the thumb very flexible. The hand needs to adapt to the specific movements, so I recommend not to overdo practicing within the first few weeks.
@ajspiano: the measures 30-32 and 35-36 are really tough.
I found these two videos very helpful:
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Honestly they encouraged me to give this piece another try. Well, rather like a few zillions of more tries

In the second one Paul Barton demonstrates especially his practice methods for those "gruesome bars", I have tried them all out and practiced them for a while and I found them helpful.
Of course, if you watch those videos, it seems like all this could be done in a few days, but it's rather months, or years.
@ frankiisko: thank you so much for your comments! I know Godowsky's versions, but so far I couldn't warm towards them. I very much respect those who tackle them, but I prefer Chopin's originals. To me they are similar to Bach, especially op. 10 no1, no.2 and no. 4. There is not one single unnecessary note in them.
I am thinking and experimenting about that pause between the end of the arpeggio [right hand] and the left hand octave.
@ Hakki: thank you very much for listening and for your comments!
I think it's really difficult to play this Etude note-perfect. Even Ashkenazy in his legendary live performance has one minor slip! I listened to it in slow motion and I think it's really ONLY one! Which is legendary, of course.
I also hope I can post a better version than this one in the future. It's a lot about relaxation and letting it flow (and unleash the fire), but you need a lot of preparation to get to that point.