In the survey template you can add the below style to the CSS box to limit the width of your  matrix question.

To widen a matrix so that the columns are even: (you would set the column width on the edit item page) 
To over-ride that with the survey template add the below to the CSS box:
.MatrixDynamic{width:1300px;} 

(1300px is the width in pixels of the entire matrix question)

To change the width of the first column of the matrix:
.SurveyMatrixHeadingRowText{width:350px;}