My client wants the input fields to display wider; because the columns are set up as a percentage of the total width, I can't seem to make them wider. I did create/add custom CSS to position the items within the columns, and I would be fine if the tables got wider and filled the full width of the page, but I can't figure out where to set that.

If I used Firefox to find the the styles, and found this:
#docContainer.fb-large .column {
margin: 0;
padding: 0 7%;
}
#docContainer .column {
margin: 0;
padding: 0 6%;
}

If I turn off the padding in Firebug, the form will go the full width, but if I paste these into my custom stylesheet, change the padding to 0, add "! important", then look at it on my development server, no changes take place.

I'd appreciate any help in this.

Are you using a responsive form? A link may help.