I have a multiple choice question that each choice has a different weight and the maximum total score for the question is 1.67.
So, in the first picture attached if the respondent select the first and second choices. His total score would be 0.42 + 0.42 = 0.84 for example.
If he selects the first, fourth, and fiveth. His total score would be 0.42 +0.83 + 0.83 = 1.67, because the maximum score for the entire question is 1.67.

How can I set this condition in detail?

Also, when I export the survey's answers to excel, they come as showed in the second picture, but I need that the answers come as showed in the third picture. 
How can I set that?

I think it would be easiest to do this in Excel: =a1*0.42 +a2*0.42 + a3*0.42 ...