getting hihats to work properly is the bane of electronic drum triggering.
the 2Box brain sends three different MIDI messages to represent hihat data, these are the default settings:
MIDI Note #45 for bow hits (what BFD refers to as 'tip')
MIDI Note #46 for edge hits (BFD calls these 'shank')
MIDI Control Change (CC) #01 to indicate the pedal height (0–126; 0 = pedal up, 126 = pedal down)
CC #01 is the Modulation Wheel message, the other common message used is CC #04, which is Foot Control.
note that the 2Box only sends the pedal height CC when you hit the hihat, not continuously like most other drum modules. in this respect, it is like the Roland TD-20.
i don't have Superior Drummer, but i doubt you will be able to get the hihat working with just MIDI learn. look up variable hihats in the manual...