This KB has the current Missing Sync for BlackBerry contact field syncing breakdown:
https://support.markspace.com/index....=70&nav=0,3,76
Only one address/number per field label in Address Book syncs to the BlackBerry.
Also, Email Address mapping: The BlackBerry has a limit of 3 emails per contact. Missing Sync for BlackBerry will sync the first three emails in Address Book per contact to the device. (This was current as of BlackBerry OS 4.2.x)
Custom fields are not supported from Address Book, because there is no user controllable mapping of the fields.
Hope that helps. If you need more help/info, let me know.