in regard to your first question, i think you will need to set the border on the contentWrapper div, this will not add a border around your footer. this should be listed in your tree structure.
in regard to creating the faux column and adding a new div, those are features that are only available in Sculptor v2.
To store your css in separate files, make sure to always select the Output tab and specify the css files where you want to css to be placed.