Hello There,
Thanks for posting in!
I have inspected your page and the column container is already fullwidth. Your image has a width and its own maximum width. It has exceed the bounds of the column container already. It is suppose to be only 100% so that the image will be inside the bound of column container. The problem is not the column container. Your negative margins/paddings and the way you have set up the row and column layout is completely incorrect. You only need a section, a row and a two column section. The first column will have the text contents and the other column will have the image. I completely understand why you have gone this way because you wanted to have a 3 columns to house the 3 icons. You can use the block grid element instead. So the left column would probably have these elements:
headline element
line element
headline element
headline element
line element
block grid (3 columns)
headline element
line element
button element
I would recommend that you check out this video tutorial on how you can have a multi column inside Cornerstone:
If you can give us access to the site, we would be happy to demonstrate how you can layout the section using the suggested idea.
Best Regards.