I have adjusted my survey to span 70% of the window with the following code:
.Skin .SkinInner{width: 70% !important;;
max-width: 70% !important;}
While this works for majority of the survey, there are questions that still do not correctly span the window despite the forward and back arrows (and banner) spanning the window correctly. The image below is an instance of this. The issue occurs with matrix questions and a dropdown question.