[robespierre]

scsi(0) is the internal bus on Indigo2, scsi(1) is external. The Indy (the machine shown in that video) has only one bus, scsi(0), which is both internal and external.
The problem is at your Step 5. "The screen becomes black" can mean that your monitor does not like the video signal. It's important to know that the firmware ("prom") and the IRIX system use different signal frequencies for graphics output. You could alternatively try running from a serial console to see if the kernel loads successfully.

edit: I see you tried that. Is that error coming when you type "2" to install software and choose the CDROM #4 as the source? I would check to see if you have a hardware fault using the diagnostics. From the prom console, type "dksc(1,4,8)ide.IP22" and see what it reports.
Also, you don't show your machine's configuration. It can be useful for finding problems.