+1 on what curbtender said about some wobble being common and evident when the wheel is spun backwards as you were doing. That wobble should not be evident when peddling forward as you normally do when riding since the pawls inside the freewheel/freehub engage the hub in a solid manner in order to propel the wheel. Likely the best you can do is to flush and reoil it which has been covered many times. Else try new hub. Also +1 on supcom's comment. Right on!
P.S. to some freewheel noise is a sign of quality since some of the most expensive hubs are the noisyest.