Okay, so after looking at your demo, there's a couple things you can do.
The easiest method is to simply float
#block-block-16 right, float
.page-header left, set
clear: both, and be done with it.
But that's not great because we are kinda circumventing
$('#block-block-16, h1.page-header').wrapAll('<div id="top-container" class="clearfix"></div>');
From here, again we'll just float the buttons right and the page header left as before.
We can also take care of some details and clearfix the new div (included in the JS) and perhaps change our bottom border from being set on the h1 to being set on our new div, so that it stretches across the page, below the header and buttons.
You may also choose to remove the 9px padding-bottom on the h1 and instead change that to a 9px padding-top on
Hope that helps!