Perhaps just comment out that line and test again, and give us a chance to test it here. E.g.
<font color='"#FF0000"'><!--</font> <link rel="stylesheet" href="/zandbak/templates/sublim_7/css/template.responsive.css" media="all"> <font color='"#FF0000"'>--></font>
Are you sure you are just removing that one line? I don't believe that could have an effect on the server. It's just one less thing for the server to do.
Trying to change the styles in that CSS file would be a huge PITA. Another option (at least for testing) would be to leave the file there but just comment out all the code. E.g.
[I]all CSS code here[/I]