Do an analysis of the chords that the notes form, then work hands seperate in short sections (2-4 measures at first), paying close attention to details. Once each hand is secure in what is played, put hands together. When you put hands together, though, go slow and MAKE SURE that NONE of the details you worked out in hands seperate practice are lost.
The short note sections are called
cadenzas, they are like short interludes between different variations of the theme.
Sight-reading is improved best by simply practicing sight-reading. It does help to be able to recognize patterns and chords, but if you don't keep grinding away trying to sight read new pieces, you won't significantly improve.
Looking at both clefs simultaniously is a skill that will come with time, as well. The eyes have the ability to do this, much like our peripheral vision helps us see more at a time. The more sight reading you do, the easier it will be to recognize notes in both clefs simultaniously.
Spend some extra time on the cadenzas, there's no reason to plow through them at first. Learn the proper technique and fingering for them and start slowly, gradually working them up to speed using various methods of practice.
Sight read a Chopin etude??? While I'd say it's definitely possible to do this if your name happens to be, say, Franz Liszt, but why on earth would you want to do that anyway? The very definition of "etude" implies that they are meant to be studied, not simply sightread. There's simply too much going on to gain anything useful from sightreading the etudes. For getting more experience sight reading, I'd recommend you try something a bit easier to deal with than etudes.
Hope this helps a little.
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