3, well, goto about:config and change the value of browser.tabs.loadDivertedInBackground to true, Im not sure why this has anything to do with youtube tho.
1+2, well, let me just say, you won some, you lose some, its a balance, you can weigh for yourself.
thank you
Ya that still doesnt work with youtube. That and the zoom make me dislike firefox sometimes. I love the idea of OSS, and I try to use it over proprietary stuff, like webkit nightlys over safari.