Your scsi.device is not in the Kickstart but in the 7.0 Roms on the 2091 (iirc). It sound a little like a termination problem, as audio CD's don't send any (or much) data through the SCSI bus.
You might also have a look at the SCSI chip (WD). Install the latest version you have (preferably a rev -8).
Does the drive work if you boot the machine with the CD already loaded?
Also mark your HD as "last drive/last lun" so your controller won't scan the rest of the SCSI bus (de CD-Rom drive will still work fine from WB)
