Grid width, can be changed under Theme options > Global > Advanced section and it's not true that nothing changes. We did tested this option yesterday few times and it works. If nothing change on your side, make sure that you do not use any cache stuff and also please remove all your extra plugins.
If you use cache plugin, you should know that you won't be able to do changes until you will not clear the cache or in some cases even clear cache and deactivate plugin. This plugin is very extensive and even we do not know all it's configuration possibilities. That's why we don't know what could be wrong on your side unfortunately. We can only tell you that in the past when we were configuring this plugin, we had some problems on server side and our admin fixed them for us as it's sometimes necessary to install missing libraries to change server configuration. W3Total Cache plugin is not easy in use and sometimes needs changes on server side.
Comments
Thanks for understanding!