Changing #innerrim width?

Trying to change the #innerrim from a width of 1200px to 1000px (just for desktop view)- but when I do, the sidebar scoots to the top of the page, instead of being on the left, where it should be. How do I make sure that the sidebar stays put? Here’s the code I put in the CSS tab:

#innerrim {
width: 1000px;
float: none;
margin: 0px auto; }

Here’s the site:
https://blueoakwebdesign.com/Wordpress2/