BB Bold 9700 :: All Calendars But No Tasks Showing

I have been through the many Google synching problems already and finally managed to get the calendar going as planned. However since last week all the entries are now showing twice, one in my "google calendar" and the same entry again in my "device" calendar. I would like to only show one of them as the default, but I can't set a default evidently, so in order to show the entries once only I need to select the calendar manually each time.
How can I

a.) get rid of the duplicates - or alternatively

b.) show one calendar as the default

c.) sync my tasks and show them on the calendar?