Fixed it using number_format() and tweaked it so that the ratio in theme options are respected, quite far from perfect but it’ll do for me.
<?php $sidebar_right_padding = 1.46; // 16px gap between content-sidebar-wrap and right-sidebar in % relative to #container ?>
<?php $sidebar_left_padding = 16/(1092-(1092*$sidebar_right_width/100))*100 ; // 16px sidebar left padding relative to content-sidebar-wrap ?>
<?php $content_padding = 42/(1092-(1092*$sidebar_right_width/100))*100; // left + right padding + 2px buffer relative to content-sidebar-wrap ?>
<?php $sidebar_left_width = $sidebar_left_width * 100 / (100 - ($sidebar_right_width+$sidebar_right_padding)) ; // left side bar relative to content-sidebar-wrap ?>
.content-sidebar-wrap {
width:<?php echo number_format(100 - ($sidebar_right_width + $sidebar_right_padding),2); ?>%;
}
.page-template-template-sidebar-content-sidebar-php .content-sidebar-wrap #content {
width:<?php echo number_format(100 - $content_padding - ($sidebar_left_width+$sidebar_left_padding),2); ?>%;
}
.page-template-template-sidebar-content-sidebar-php #sidebar-left {
width:<?php echo number_format($sidebar_left_width,2); ?>%;
padding-right: <?php echo number_format($sidebar_left_padding,2); ?>%;
}
.page-template-template-sidebar-content-sidebar-php #sidebar-right {
width:<?php echo number_format($sidebar_right_width,2); ?>%;
}