1. As APU fuel is normally included as part if the taxi fuel, it would be part of Ramp or Block Fuel. Extra fuel is exactly what it says on the tin. Fuel that is in excess of everything that is planned to be burnt.
2. The most important function of the APU following an engine failure in a twin is to provide an additional generator, not bleed air. It's fuel will be supplied from whatever source is available.
And referring to my comment in an additional thread, you really need to get some more (lots more) time in aircraft, preferably under supervision. Also, you will not make it in an A320. It will be too fast for you and your knowledge will be found lacking. Furthermore, should you find yourself in the left hand seat of one in the near future, you will be working for an operator who will have lethally low standards.
I do admire you asking the questions you do but you must do your training in a structured classroom environment, not on an Internet forum with information from un-attested, unregulated and anonymous sources.
So where should you go next? You must find an operator with instructors and a range of aircraft from singles to twins. When you are earning a living flying a piston twin, then, and only then start thinking about a jump to a turbo-prop and after that an A320. It's either that or pay for a considerable amount of Procedure Training (sophisticated cardboard bomber) under supervision, and the key bit is 'supervision'.