I would try reducing PG level as well.  I've had clients who complained about the same issue,  I ended up reducing both nic and pg levels to fix it.  As for the craving for nicotine lowering over time,  it's true.  Something a lot don't realize is that tobacco contains 4 other addictive chemicals that are directly related to nicotine,  and addictive like nicotine.  Nornicotine,  Myosmine,  Cotinine and Anabasine.  Nornicotine when in processed or cured tobacco becomes a carcinogen,  and still addictive.  So when you finish withdrawing from these,  all that's left is the Nicotine,  and it isn't nearly as addictive as you might think by itself.