I concur with everything but your second sentence :
He got slow because he pulled some pitch up and even converted some of its kinetic energy into height.
Trimming into an airspeed with a gliding airbus is simple : just do nothing and the aircraft will maintain its pitch angle, speed will then progressively stabilize at the speed which corresponds to this pitch angle.
If this chosen pitch angle is too high then yes, the speed protection will come into play.
The APU is useful in maintaining alive all the electrics and hydraulics. Guaranteeing optimum manoeuvrability.