It looks like those symlinks are right. Does the command "/bin/passwd" work? If not I would cd to
/opt/K/SCO/Unix/5.0.5Eb/bin/ and look around. Like what does "ls -l *passwd*" report? If your passwd command has been corrupted, I would guess that you've been hacked. You might need to re-install the os to be sure you're ok. But if you have a second sco box, maybe you could try copying the executable.