Referring to FCOM PER-FPL-QFP-40-A
Why not try with just one stop? Assuming 2,5t to land with.
With 18t of payload:
. 41t DOW
. 59t ZFW
. 61,5t LW
. 77t TOW limiting
we get 15,5 t of fuel to use > that is 2700 NM (6h15m)
With 0 payload
. 41t DOW
. 41t ZFW
. 43,5 LW
. 2700 NM mission segment
we need 11700 kgs to make it, and 150 for taxi.
PS: what was the core of question again?