I have worked on opus10 no7 many years. The crucial fingering in the inner voice (repeated notes) involves the thumb and index. For some years I played it: 2,1 - as indicated in all editions. One day, I tried playing it with: 1,2. This seemed to solve the problem, but then once again after a few years, I reverted to: 2,1. And it seemed MUCH easier than the first time I used this fingering.
The fingering of the upper voice has also problems. After years, I have still not decided on what fingers to use for the more stretchy intervals! Generally, I can say that playing the piece mezzo-staccato (as also with opus25 no6)solves many problems. And with mezzo-staccato, it sounds MORE legato!
Of course the instrument and acoustics of the room are terribly important. Also, to work with an open lid, assures quicker response to the sounds. An open lid does NOT mean loud playing. I find the only way to play pianissimo is to have the lid opened full. Only with an open lid will my ears respond sensitively to the sounds. Also do not overlook the fact Chopin wrote his music on the light-actioned Erard or Pleyel. The touch on modern pianos is perhaps twice as heavy! I know from personal experience of both.
San-Ying.