Rescue photos from TF300T via Fastboot or APX? An older backup exists but ADB is off

Hello, my TF300T went into rebooting and gets stuck at ASUS logo ever since. Hard resets, RCK etc. do not solve the issue. Unfortunately, it occurred on a rather unique trip, and I need to recover photos and videos prior to wiping data.
I'm new to Android and reside far from the country of purchase. In my previous experience ASUS remote support is mostly irrelevant and occasionally plain wrong. So your advice will be greatly appreciated.

The pad was not rooted and retains the original bootloader; the firmware version is the latest official one (us_epad-10.4.2.17). "USB debugging" was off -> the tablet is listed in "fastboot devices" but not via ADB. With Naked drivers installed in WinXP, its Device Manager detects the pad when started in APX mode. I also have an external backup of the system made via ADB a couple of months ago (firmware US_epad-10.4.2.9 which is an earlier version of the same Android JB; please see attachment for details).

Is there a way to recover my camera shots by extracting them via APX or Fastboot/replacing some files or directories in the pad with those from the backup/reflashing firmware without wiping user data (if that is possible)/waiting for the next software update and installing it manually/using another method?

Many thanks in advance!
(Of course, the moderators are welcome to fix tags or move the message if necessary)

UPDATE: Attempted updating the tablet via Fastboot with the blob from the next software release by ASUS. No errors during the update; upon a restart the pad reported something like "reconfiguring applications". The corresponding bar completed its progress, but then TF300 got stuck again at ASUS logo/throbbing circle. Selecting RCK with the entire update on a microSD card yielded a dead droid...
Repeating the aforementioned steps and erasing /cache did not solve the problem, so I ran out of ideas. "WIPE DATA" seems to have revived the pad for the time being. All in all, a fairly frustrating experience of 4 dataloss crashes in a few months of light use of a stock-configured tablet (which cannot even be set to shoot directly to an SD card).

The rather obvious lessons learned:

• backup important data to external memory immediately;
• have not tested pulling data via ADB yet, but keeping USB debugging on might be useful (even if it costs some battery life, as I read somewhere).