Can you attach a sample workbook?
Maybe someone else will chime in, but I think you'll need to revisit your data structure. Tableau can easily add the 'Totals', but I don't think there's much it can do for rows with missing information on a reasonable or expandable level.
Here's a potential structure. I added a quarter date and metric value field that moved the fields into a long table (more rows, less columns). As you can see I also repeated the Internal Sponsor Name and Sponsor Name records for each time they appeared.Personally, I would also change quarter_date to an actual date (01/01/2018 = Q1). Tableau can display Q1 if that's what you require.