Yes there is a way to limit the max number of each layout. When editing the layout, below the layout label and name are 3 additional fields including “Min” and “Max” these are for setting the minimum and maximum number of this layout that can be inserted.
As far as the related question, this topic has come up may times. http://support.advancedcustomfields.com/forums/search?bbp_search=reusable+group
