Re your question re Taxi Fuel.
Normally each Operator has his own figure for Taxi fuel as agreed with the appropriate Civil Aviation Aurthority it does vary from Operator to Operator and certain Airports i e some Operators have a higher Taxi fuel for certain Airports where they know there will be a long Taxi time i e JFK.
Normally though the Taxi fuel is a small percentage of the total fuel that is legally required to be carried for the Flight.
Sorry cant be more helpful but you will need to have sight of the Operations Manual for that particular Airline in which you are intrested.
Regards