Hi Jim,
CSS changes in different versions of Artisteer so you have to figure out what you are trying to override and it is not the same for each version of Artisteer. In recent versions of Artisteer the class names are all lower case and CSS is case sensitive so .art-contentLayout is a mistake, it would be .art-contentlayout, but actually you don't even need that as part of the selector.
I was able to get it working her by adding this instead of what you have in style-artisteeroverrides.css:
body.homepage .art-content{width: 650px;}
body.homepage .art-sidebar1{width: 270px;}
body.homepage .art-sidebar2{width: 330px;}
body.homepage .art-content-wide{width: 782px;}
body.homepage .art-content-narrow{width: 383px;}
body.homepage .art-content-layout .art-sidebar1::before { width: 275px; }
body.homepage .art-content-layout .art-sidebar2::before { width: 335px; }
note that without the bottom 2 it was overflowing the different shade of green for the side bar background colors so I had to figure out which selectors from the artisteer css were causing that using "Inspect Element" in Chrome.
Hope that helps,
Joe