Item 1, SCSI.
The connector to external devices is just an extension of the SCSI board. Yes you must have cuidadocon terminator in the devices properly placed operates a chain SCSi smoothly. I use the external connector through an HD and CDROM. If I remember correctly, if you install an internal HD the system assigns the ID 1, the Floppy ID 0 and any external device is assigned the ID 2 onwards. Floppy ID0, ID1 HD HD IN OUT ID2, ID3 CDROM OUT ..... up to 3 more devices. You should put terminator on the internal HD and only the last device or external chain.
Check out the model of your drive and will leave doubts as to manually configuring the ID using jumpers. Even you may have terminators automated resistance. I guess it's a Quantum ProDrive.
Point 2 Stereo.
This is the configuration of my EMAX II mod, 2212 extended to 8 MB
IC9 empty IC10 IN> Stereo
IN IC9 empty IC10> Mono
None of the IC> Shit! Unusable.