Dora - to get your date on Columns, just switch the DAY(Week Ending On) pill on Columns to "Exact Date" and then change it again to "Discrete"
It sounds like you're essentially looking for a Grand Total across all Apps, but you want that number on top instead of on the bottom, where we normally place it - there may be some tricky ways to do this table calculations, but I personally would just something like a UNION in your Custom SQL...just create a second SELECT statement which generates a SUM() of this measure across rows, and name it "Global":
SELECT 'Global' as App, SUM(Measure) as totalAcitve,....FROM Table
You'd then need to either do a manual sort to get this "new row" on top - or do something fun with an additional numeric column you add to your query to enable a more dynamic sort
If you don't mind "Global" being the last row, then life is easy. Just turn Grand Totals on, then Format the label and change the Label property at the bottom of the Header tab to "Global" from it's original "Grand Total" text.
Hope this helps a little - some of the other folks who work more on "formatting" may have better ideas, too.