Hmm. The FM-Bochs source doesn't look like SCSI-1, it's probably custom.
Yes, looks that way. I've found a list of IRQs for the FM-Towns, and it shows the SCSI controller and CD-ROM controller to have different IRQs (SCSI is IRQ8, CD-ROM is IRQ9). SCSI is likely to be used for HDD, something the system doesn't require (most software boots from either floppy or CD-ROM). There's also Linux/Towns source for me to look through to get a decent idea some more of the functionality.