No it doesn't; read the license again. It disarms you from being the aggressor; if FB comes after you, you keep your right to counter-sue while also keeping your license to use the software.
Yes it does, Them using patents that you don't grant them and you being unable to sue them for it is definitely putting the power in their hands.
Yes, that's exactly the point. It disarms people from fighting over patent nonsense. If you hate software patents you should love the bad + patents license.
Facebook could never take away your license to the software. BSD license was irrevocable, whether you sued them or not.