That's really great! Thank you for the detailed answer, very much appreciated, really. I already installed the Jailbreak + Bridge and managed to connect with my local Cygwin configuration via SSH and the NDIS bridge to the Kindle and have access to the root account. So there it is, "basically" my safety net. Now I wanted to backup my partition 1 and 2 but have slight problems
I assumed that my host IP address relative to the Kindle would be 192.168.15.1 because that's how the SSH connection is established, but when directing the dd output to that address / port the whole thing just freezes and does nothing -- out of desperation and creeping suspicions that I don't understand networking at all I also tried the local IPV4 address within the home network (192.168.0.17) which is unreachable. If this gets too offtopic, I understand, I'll take it somewhere else -- I just thought if it's something glaringly obvious, even if you guys aren't running Windows you might be able to tip me off. I guess I could just backup the partitions to the user storage on the device but... meh.
Anyways, thank you so much!