How can i move it back? Rated 3 out of 5 stars

"It does work with Firefox 6 - it's now found in Tools->Web Developer."

How can i have this icon in "tools" without this "Web DEveloper"-Submenu?

This review is for a previous version of the add-on (2.0.7). 

Yes, it's moved in Web Developer along with other tools like Firebug. You can alternatively put it in your toolbar: http://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars