That board isn't compatible. Line 6 used to make the FBV Longboard that had two onboard expression pedals, but I'm nearly certain that it isn't officially supported as working with Amplifi, either. I do imagine, though, that it could be used to change presets and turn effects on and off, but you'd also have a lot of buttons that don't do anything. I'm not sure if the two pedal would work separately as volume and wah or not.
The official supported way to do what you want is to get one of the FBV pedals, either the older ones or MKii versions. The FBV MKii controller allows to you add an external expression pedal. So that would be the way to separate wah and volume.
Time is a train
Makes the future the past
Leaves you standing in the station
Your face pressed up against the glass