Learn much, you will.

1)  The Ernie Ball is just a straight volume pedal right?  If so, it it not really designed to be used as an expression pedal.  They come in 25K (Active) and 250K (Passive) versions and have an input and an output.  The expression pedals required for a POD have just a single connection and has a 10K Pot inside it.   I have seen hacks on the web that allow you to modify a volume pedal to work as an expression pedal but out of the box:  no.

You can still use the volume pedal as a volume pedal eiither on one or both of the two channels that you intend to use and use the built in pedal to do your cross channel fade

2)  There is no magic bullet for balancing off the presets.  It must be done manually.   The way I approach it is to use the looper: 

• I put the looper in the post position and change to my cleanest preset first (i.e. the most dynamic).. 
• I set the volume to something sensible then record a loop using a hard  strummed chord sequence to get the loudest clean sound that I am likely to work with. 
• With the looper still running: I then change to each of the other patches that I use and play hard over the top of the loop.  I  manually adjust  each patch bolume so that the two tones sit at the same percieved volume level.

This will get your patches into the right ballpark but make sure you leave some upward adjustment on the volume knob for each patch so that you can make a quick correction come gig time.  I try and set most of my patches around 60/70% volume for this reason.  I can use the mixer and/or studio EQs to boost/cut the signal and vive me that adjustment on the volume knob (if you get me).