The “math” part, following this suggestion (with a more precise explanation here), could be solved by adding a field ("Results") to your Answers table with this formula :
Answers.Filter(Group=thisRow.Group).Answer.Sort(False()).Slice(0,2).Sum()
I’m not sure though if it was really what you were looking for (in terms of where to have those results)
But I’ll admit that I couldn’t find a logical way to get those Results as a table 
.
(I didn’t have much time to really look at all this, sorry)