Both of your questions boil down to modifying the CSS.
For Fire Fox, there is a great extension called Firebug
It is a developers debugging tool. using fire fox, you can inspect elements of the page and see the CSS for the selected element. You can also edit the CSS to see your changes applied for testing, before you edit the css file directly.
You can use fire bug to find the CSS that sets the form width to be able to edit it, and also find the css for the other form elements.