I have a similar valueexpression that adds on the following after your first comma (so delete everything after the first comma and add the following):
IF({status}="DED","N/A",IF({status}!="CPL",CONCAT("Due ",{plannedCompletionDate}),CONCAT("Completed ",{actualCompletionDate}))))
(i.e. -- if it's cancelled, display "N/A"; if it is not complete, display "Due plannedDate"; for everything else, display "Completed actualDate")
At the very least, this will show you some syntax which you can then amend to display closer to what you would like.