Does the additional patent grant in the Facebook BSD+Patents license terminate if I create a competing product?
No.
Does the additional patent grant in the Facebook BSD+Patents license terminate if I sue Facebook for something other than patent infringement?
No.
Does the additional patent grant in the Facebook BSD+Patents license terminate if Facebook sues me for patent infringement first, and then I respond with a patent counterclaim against Facebook?
No, unless your patent counterclaim is related to Facebook's software licensed under the Facebook BSD+Patents license.
Does termination of the additional patent grant in the Facebook BSD+Patents license cause the copyright license to also terminate?
No.
Does the additional patent grant in the Facebook BSD+Patents license terminate if I sue Facebook for something other than patent infringement?
No.
Does the additional patent grant in the Facebook BSD+Patents license terminate if Facebook sues me for patent infringement first, and then I respond with a patent counterclaim against Facebook?
No, unless your patent counterclaim is related to Facebook's software licensed under the Facebook BSD+Patents license.
Does termination of the additional patent grant in the Facebook BSD+Patents license cause the copyright license to also terminate?
No.
From: https://code.facebook.com/pages/850928938376556