For the first scenerio you described, I got something from the Musicom's manual:
"The EFX Mk III contains a XPDL port for expression pedal input or external foot switch input. This can be used to alter parameters(via MIDI) in effects device that offer this capability. The MIDI Control Change Value is transmitted corresponding to the position of expression pedal or external foot switch"
However, it may be that it can only transit CCs on 1 channel at a time. My reasoning for this is because if you go to Page 12 and look at the diagram, you only see 1 CCs column. Please have a look:
