Hello!
Sorry, I noticed that I've forgotten the subject!
Actually I never used the controller functions in fluid~ or fluidsynth, so I don't really know, what they are supposed to do. The fluid~ external just delivers the CC messages to the fluidsynth library where they hopefully do something. Can you test, if the fluidsynth command line application reacts somehow to your pedal?
Yes, if I play the soundfonts with the commandline application the pedal works fine. Maybe my fluid~ is too old ? (I think 0.1, but I didn't find the version really)
Thank you, LG Georg