Hi, R Schreiber (a.k.a. Mr. Quick Fix )
You have a max-width in ems assigned to the page wrapper. If one zooms the font size, the images remain their natural size but the width of this container changes. It's better to allow the container to "go with the flow" when possible. In this case, you may want to try width or max-width:1320px. See if that is more to your liking.
<font color='red'>max-width: 96em; /* try ~1320px */</font>
The next item is the position:fixed menu. It's container has a fixed width, but the menu has no width. Give it a width and it will stay within its apparent area.
list-style: none outside none;
<font color='blue'>width: 300px; /* add me */</font>
FYI: If the font size is zoomed large enough, the position:fixed menu can overflow the viewport and will not be viewable until the user reduces his font size. Be aware that this is a limitation of position fixed objects.
Hope this is quick enough.