Hmm tried that way!
moved the existing paramater file to .bac and palced the new. In AndroidTool I chose my backups as you described in an erlier post.

After flashing everything including LowerFormat the device ony boots into recovery with black screen and AndroidTool sais: Found one LOADER device. But never boots into OS.

I'm flashing now once more to verify. Do you have an idea?

Yeah I know. Since all this broke the warranty I guess, I'd like to make it look at least "un-optimized".

I managed to get the system.img in there. It does not boot properly, but hangs on the default boot splash.
Only thing is that it still has CWM active when booting into recovery. Cant I simply restore the default recovery.img by flashing my backup?

I tried with AndroidTool and it only took a few seconds. but after rebooting still CWM comes up.

Thanks much

Hey Oma,

thanks for all your support. I got the broken tablet refunded. If you dont mind, I'll send you a small donation via Paypal for your support. Feel free to PM me your id.
Again: Thanks much for your time and support.

PS: In the meantime I've bought a used Nexus 7 (2012) which works quite well for my use-case (wall-mounted to act as home automation input device).