I just received your logs. There are several things regarding what you're trying to do here.
First thing, the way you are trying to use the external directories inclusion is counter-effective and unsupported. You are trying to backup multiple Joomla! web sites by using the external directories and extra databases definitions. However, when you try to restore this backup, you will have to do so manual, as ABI is only able to update a single configuration.php file, namely the one from the main website (the one where the backup was launched from). It's best to setup one backup run for each site you want to backup. After all, there is no domain installation limit for Akeeba Backup.
The second thing I have to warn you about is that you seem to be running the backup on a 32-bit server. Unfortunately, PHP has an inherent limitation. On 32-bit systems it can only be used to reliably create files up to 2Gb in size. Anything over that and all bets are off. On the other hand, on 64-bit systems the maximum file size is in the range of several petabytes, which is practically unlimited by today's standards. If you try to create a backup archive over 2Gb on 32-bit PHP, the internal file pointers get corrupt on files around the 2Gb boundary and any extraction software (including Akeeba eXtract Wizard) will choke on them somewhere near this 2Gb limit.
I suggest that you install Akeeba Backup on each of your sites and create a backup profile for each of them. You can then either use a CRON job to back them all up, or use Akeeba Remote Control for a single-click solution to backing up and downloading the backup archives of all of your sites - or even scheduling this! - from your local PC.
Nicholas K. Dionysopoulos
Lead Developer and Director
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