Now, because in the first column of your table you want to have both lines and groups (rather than having two columns) you need to create a new dimension which has both. In this new dimension each Line needs to associate with itself and each Group needs to associate with each line. It requires that there is a 1-to-1 relationship between Line and Group.
You can create this new dimension with a pair of RESIDENT loads:
NewDimension: LOAD DISTINCT 'Line' as LineType, Line, Line as [Line and Total] RESIDENT MyData;
LOAD DISTINCT 'Group' as LineType, Line, Group as [Line and Total] RESIDENT MyData;
Once you have that you can use the Line and Total dimension in your chart, instead of line, and you will have the totals in there also. It's important that you get the sort order right, so that you sort by Group, then LineType and finally Line to get things in the right order.
Your absolute columns should then give the correct totals without doing anything else. You should be able to change the text to be bold and the background colour on the total lines, by looking at the LineType field.
To get the contribution percentages you need to do the following expression:
sum(Value) / sum(total <Group> Value)
You can then add the set analysis to get the correct periods for P1 and P2 columns.