For the first problem, try adding this:
border-bottom: 1px solid black;
border-left: 1px solid black;
border-right: 1px solid black;
box-shadow: 0 0 20px 3px #000000;
margin: auto; width: 800px;
So what do you want to do, then? It's not quite clear. Perhaps try top and bottom margin.
Another thing I have been trying to achieve is some padding on the links in the nav bar. I don't want to pad the links down, as it would make a ghost area clickable underneath the nav area.