I dont believe the limitation is in the Pro 3, but rather in MIDI OX. It will not let me select more than 1 sysex file at once. It doesn't matter if you set up the settings to make a delay between them. I read and followed the instructions carefully. It simply said load all of the wavetables, but it didn't say how to load multiple.
In the end I just loaded them 1 at a time. All sorted now.