You need atapi.device in Devs: and the FindDevice program. No CD0 or IDEfix or anything else needed to test this. Remove the IDEfix lines from your startup-sequence. It is not needed for CD-ROM access. If FindDevice does not find the CD-ROM on atapi.device, it is not connected properly. Also enable the "show all drive types" checkbox. Perhaps the drive identifies itself as magneto-optical device instead of a CD-ROM.
You could try the HDD as slave and the CD-ROM as master, just for fun. Perhaps it works better then. Also read your HDD's documentation. For some HDDs there are different settings for master with and without slave. You need master with slave present.
Finally try to start HDToolbox and click on your HDD. If it tells you there have been drives added or removed, click on Save.
Once FindDevice shows your drive you can start to configure the CD0 file in Devs/Dosdrivers.
Bye,
Thomas