I dont want to sound like a broken record here, but vBulletin has paid subsriptions built in for that eventuality
Payment gateways are
PayPal
Nochex
WorldPay
Authorize.net
the vB board also offers superior admin and mod status,
There is a super moderator and admins can be given different level of permissions
The best way to take a look at the admin section of a vB board is to look here
Demo admin panel here
http://www.vbulletin.com/admindemo.php
Manual here
http://www.vbulletin.com/docs/html/
Put in your name and email, they will then give you a username and password to access the admin demo site
Then when in the vbulletin demo site access the admin panel (top right) with
username: Admin
Password: admin
Take a look
phpBB is excellent for a free piece of kit and i cant knock it as i have used it many times.
If you want to see your site running (board77) on vB then let me know and if someone can ftp me the database i can set a test one up for you with password access only (my vB license requires this)
On the backup front then this can be setup on a cron job (automatic) but with a site of 300MB which will only grow having this automatically emailed to members would be a problem for not only timeouts but mail box limits!
300mB would have to be ftp'd for a good success rate, other thank that the backup would have to be broken into manageable chunks and emailed.
You could have it set to email members when a full backup is taken and give them a link to download it by ftp once a week perhaps
Then have the system do an incremental backup daily or 6,12,18 hourly and automatically email this to those 4 members...
You can also have a specific page built ie
www.board77.com/forum/backupnow.php
This would run a backup immediately and then it would be available as an ftp download, meaning any group of members with the password for the ftp and backup now url could run a backup and download it reagrdless of how the automatic cron job was set up!
Cheers
Dave