Hello,
Currently there's no way to set applet to other width and it'd require quite a lot of work to implement that.
However, if you're stretching it so far as to all columns, then the full-screen is defiantly the way to go. In full-screen mode ActionBar (toolbar) is there, only that it's not populated with Quick Access buttons, like contacts, companies etc. For majority of modules, they use ActionBar for its own purposes and those button would take up precious space. All the modules are still accessible from Launchpad and Menu.
If you want, you can consider adding contacts, companies etc. buttons to ActionBar in your module full-screen mode. It's closest it can really get without hijacking ActionBar module to display those buttons in othr modules, not only Dashboard.
Hope this helps,
Arek