Install this addon

https://addons.mozilla.org/en-US/firefox/addon/open-bookmarks-in-new-tab/

No, that's not my problem. That's an easy fix in the Firefox settings.

I don't think that you can do that if you bookmark a link by dragging the tab on the Bookmarks Toolbar. In that case you need to press the Ctrl key before starting to drag the tab to make a copy. It should work for the current tab if you drag the favicon in the location bar on the Bookmarks Toolbar or to the sidebar.