As an example of why we need to see a site live and look at the stylesheets for ourselves, the critical factor is that you have a rule in stylesheet_y.css (line 32) which is loaded after stylesheet_flexible_attributes.css and overrides it:
#productAttributes .clearBoth {
clear: left;
display: inline;
float: right;
width: 50%;
}

This negates the rule in stylesheet_flexible_attributes.css (line 26)
.wrapperAttribsOptions + br.clearBoth {
display: none;
}