I played this work last year, and I have to tell you, it's a beautiful music, don't give up because of this problem. I can reach a tenth too.
So:
in measure 13 to 14, (the note A flat) and 15 to 16 ( note C), I play both with right hand.
In 16th measure, I played the notes C-G arpeggiated, and I think it's the only (and better ) solution. if you listen some interpretations on youtube, several pianists do it arpeggiated.
about 20 , 21 and 22, I arpeggiate all the left hand chords, except the first chord in 21 and the first chord in 22 (E flat - G). I played the G note with my right hand. It was the best solution for me.
Don't forget , when you play some passages with both hands, melody line must continues, the sound of melody can't die. The sound of each note is very important, particulary in this music.
Hope I have helped
(and sorry for my English)