I can't speak to specific aircraft without numbers .. however, generically
(a) computers can fly an unstable aircraft due to the far greater sampling rate and control input discrimination
(b) for the MIL FJ fraternity Martin Baker provides a level of redundancy
(c) for the civil world one could reliably not see other than acceptably longitudinally stable aircraft being certificated
(d) I suspect that the emphasis is on keeping the CG towards the aft region of the certificated envelope for the fuel savings
(e) the real question of interest is the pilot workload level if the automatics fail and the human pilot is required to save the show on the day
the a/c is flyable by pitch trim alone if necessary
Keep in mind that long stab is to do with the pitch stick forces and stick force gradients which the pilot perceives rather than what the controls are doing physically.