You have a beautiful tone and I like your interpretation, though I think it's a bit on the slow side. I wouldn't play it any slower than quarter note=63. This might be difficult for you to get used to at first!
The left hand can make or break this nocturne. It's one of chopin's pieces where it is definitely more important and crucial then the right hand. Start practising with the metronome a couple of times, l.h. only. Strictly in tempo until you feel that it's right for you. You've got to get that plodding sensation out of your head! Now, without the metronome, l.h. only, play it as if it were in 2. It will naturally go a little faster, but this is so you hear the melodic line of this left hand. At the end of each group of 6 notes, a little diminuendo. A rounding off, so to speak. Really practise it a lot this way, until it becomes second nature. That way, when you put your hands together, you can put everything you've got into the r.h. which you already do very well, and the left hand gives it that fluid running quality, almost like a barcarole.