Do you have a specific reason to run Server 2000? If not has there been any discussion of upgrading past this? It really needs sorting.
With regard to your points;
1) You can do this with a NAS drive and running NTBACKUP from the server and storing the backup on the NAS. If it dies you can then restore to this backup, ASSUMING that it isn't a hardware failure, and assuming you can find a replacement part for a 13 year old computer <<< Is this is realistic? If not plan to upgrade.
2) You need a "redundant" server (not a backup one, that term would be misleading in this scenario, a "backup server" would imply a server that holds your backups). Since you cannot add a 2008 server as a DC to a 2000 functional level domain you need to add a 2003 server in first, do you have access to a 2003 license?
If not I'd argue you may be better looking at buying a 2012 server and starting from...
<<< Is this is realistic? If not plan to upgrade.