the buzzing sound is probably the 'spring' that keeps the clutch in place. its normal
as far as the ghost pedaling and no slack. youll have to take it apart and see.
Your can only really take the axle out on must hubs though the non drive side. so while keeping that side together see how far the clutch gets from where the driver would be. the farther it can get, the more slack you have. In nankais and geishas there are washers that if taken out will let the clutch get farther away. adding more slack.
its vague, but look a couple of how to's on how to add slack to any freecoaster. they all work fairly the same. I think adding more slack ill fix your ghost pedaling too