The aircraft does not specifically give windshear guidance, just windshear detection.
Not really correct. The FDs when windshear is detected and TOGA is selected are specially adapted (optimised) compared to the standard SRS. Following the SRS as long as it's available will give guidance for the optimal escape manoueveure.
you can then follow the SRS FD's demands as long as you still believe you are in windshear. This can be above 1300' of course.
Not necessarily. Let's say you have a low altitude set in the FCU. The FDs may go into ALT* mode; hence the guidance to maintain 17.5° if FDs no available, and you're still in the shear.