i had a good look at this last night, its a rather hectic stylesheet. the only reference to content is full width.
i personally feel that your best solution would be to grab all content text and custom code snippets and...
maybe start from scratch. you have maybe over-complicated things.
use the latest thematic revision.
keep import to layout style in your css.
/* Apply a basic layout */
@import url('../thematic/library/layouts/2c-r-fixed.css');
all your pages will then have a sidebar on the right.
use a custom template for your home page that grids all the images, etc. that looks nice full width. you can set that as the front page.
there are several ways to achieve this using the templates and functions. you can also use dynamic classes
body.home #container {width:940px;margin:0 10px;}
body.home #content {width:940px;}
body.home .main-aside {display:none;}
if you want to change the content for sidebars on different pages, widget logic is pretty simple to achieve this (or functions.php using conditional tags).
you could also use the new wordpress3 menu system, manually add the pages and a category entitled 'blog' to display your blog.
i hope any of this helps.