Disable Dynamic Resizing Twenty Fifteen

Hello all,
I am trying to make a simple website using twenty fifteen theme. I basically have it where I want it, and I have deleted most of the dynamic resizing in the theme (why????). But there is a little left and I cant figure out how to get rid of it. I have attached an image of how I want it

always

yet two things happen:

when I drag it larger the borders and paddings change, and when I drag it smaller the left bar dissapears. how can I have it so it always looks like what it is in my image, and never changes?
Thanks!!!