I'm not sure what "bar" you are referring to? If you mean the slightly darker grey area where it says United Kingdom and has the links for settings etc. then this is an intrinsic part of the web page, you can't remove it. Can't imagine why you would want or need to? It in no way interferes with typing something into the search box which is surely the only thing you are ever going to do on the Google home page?
As for opening new tabs with Google (or any other home page you choose) there is a Firefox add-on called "New Tab Override" that enables you to do this.