[Tutorial] - Fixing a bricked system

[is0-mick]

From what you posted it seems that sdcarda6 is where your system is trying to boot from.
/dev/sdcarda6 on /system type squashfs (ro,relatime)

What you need is a good copy, or pre-patched copy of the SAME version of firmware as what was originally on your tablet.
It's no good backing up sdcarda7 as it will be a different version, as every time the system is updated it swaps between A6 and A7.

So...
1) get a good copy of firmware (same version (original or patched) as what was on your tab originally)
2) dd if=/vp_mnt/sd/goodfirmware.bin of=/dev/sdcarda6
3) app_destroyer.x -f
4) reboot.

That should do it.
Mick