I am not familiar with SCO, but the command in the crontab will "just" copy the files and directories to the device /dev/rct0, which is most probably your attached tape drive.
This type of backup is not bootable. It misses the boot sector, filesystem structure etc. which is needed, to have bootable backup. It will have your business data in there though.
You could do a copy of the disk with the command
dd which will create a file of 9GB, as larges as your disk is, because it copies all bits of your disk. It could be restored with using a bootable medium that gives you a shell from where you can issue
dd again, to restore the backup.
The hardware sounds x96 compatible so you could for example try Knoppix (
KNOPPIX - Live Linux Filesystem On CD) which is a free Linux bootable system with desktop etc. to issue restore.
Here is some guy that tried something similar:
SCO 6. Backup & Restore from USB
Maybe it is an option to get a modern x386 PC or server hardware, install a later version of SCO Unix and migrate your application overthere. It could be it is possible by simple copying it's needed files over to the new installed machine. Though I saw the latest release of SCO is 2009
OpenServer X seems to be the continued SCO Unix but I have no clue how compatible to each other.