Someone with more experience then me could probably do this with less code but I go:

header > nav > a:before { content: '♦ ' !important; color: #443311 !important; }
header > nav > ol > li > a:before { content: '← ' !important; color: #443311 !important; }
header > nav > a[href$="#new"]:before { content: '+ ' !important; color: #443311 !important; }
header > nav > a:hover:before, header > nav > ol > li > a:hover:before, header > nav > a[href$="#new"]:hover:before {
color: white !important;
}
dt > a:before { content: '♦'!important; }
dt > a.sticky:before { content: '♥' !important; }
a.delete:before { content: 'X ' !important; font-weight: bold !important; }

Also, in lines 16-23 of your code, I changed the font-family style to read like this:
font-family: verdana, sans-serif !important;

(It should be noted I couldn't find a suitable unicode icon for the rss link, so I left it as a diamond)

And concerning the underline thing, I reinstalled your original style and it was fixed. I guess I inadvertently caused the error myself :P