I can only say that vBulletin 3.5.4 should be secure enough, there are no known security issues. About the other 2 i can't make a judgement.
Back ups (if you host don't make them yet) can best be made from the shell. Beside a terminal emulation programm, no other software needed.
For instructions see the chapters in the vBulletin manual:
Backing-up your MySQL Database Manually
Restoring your MySQL Database Manually