I too am having some issues with DW CC fluid grid feature... By the way, i am not new to dreamweaver nor am I new to CSS! However, I am puzzled as to why I get all this overflowing text when I add padding or margins to elements that have no declared width... I even attempted to use border-box so that all box properties do not cause elements to grow in size.... To make matters worse, I cannot find specific documentation, all I've found is really basic stuff.
For instance, when I add margins to my paragraphs, percentage based of course and using a mobile first approach, those paragraphs overflow the parent container. In my mind, this should not be happening. When I previewed in a browser, there it was, text was overflowing its parent container just as it was in DW. (Not live view. Live view is completely inaccurate.)
Someone please enlighten me. I'm almost ready to just create my responsive site by writing all of my own code. I'd prefer to use DW CC as it could save time if the formatting would work correctly.