So, the reaction mass is not part of the rocket.
That is correct, the reaction mass is not a part of the rocket. The rocket carries the reaction mass.
When you get into a car, do you become a part of the car?
If the purpose of the car is to move in any particular direction and I am adding mass to the car, then for all intents and purposes, the answer is yes; however, I am not the reaction mass.
Define reaction mass.
Just to clarify we are understanding terms in the same fashion.
Because according to my understanding, it is the fuel
SHOT BACKWARDS in order to propel the rocket forward (i.e. opposite direction).
This also seems to be in direct contradiction to your claims the rocket is able to move in a vacuum because of pressure taking place INSIDE the rocket.