Hi seems that one of your FLAP servos is turned the wrong way physically, or rather the servo arm should be 180°
from where it is, then both servos will move in the same direction
And yes you need one spliter for the FLAPS
The Ailerons connect one to the Aileron R channel and the L Aileron to AUX1
you can off course reprogram AUXs as you wish.
You will have to chose the wing Option you would like to use in the Wing menu
Ronny