hi tangledma !
After considered your site , the class of bootstrap used does not exactly . You need to understand the define of grid class ( col-lg, col-md, col-sm, col-xs , row and container)
You can modify the break points in bootstrap to customize this but if you want to stay within the default break points of bootstrap you would use these attributes. They directly correspond to col-lg, col-md, col-sm, col-xs.