Hello,
I don't have a Nord, but I do have questions.
Are you using the Nord for MIDI playback as well as a controller?
Have you checked the Help>Logic Pro Instruments? There's a section on the Vintage B3 and use with external MIDI controllers.
Also, the Split tab on the lower right of the B3 interface gives you some additional options.
Or perhaps you already know this and need something much more specific.