Well, everything working again.
But I didn't need to fastboot, actually I tried but failed with <waiting for device>
error.This error is related with usb mounting, and I was aware that kindle was getting auto-mounted with Dolphin
even though I don't have automounting enabled in the device notifier. Googling about it I found this
maybe the filsystem corruption wasn't my fault after all.
So, how I fixed? Days ago I found I could ssh in "normal" way, withouth the diags mode, I think after installing ixtab rescue program, because I dont think I could before. Anyway I thought I could try to dd that way, and it worked!!. I thought I could not work because I get confused with normal linux systems where you can't managed partitions/filsystems that are in use, the typical error you get with gparted. Am I making any sense?
The only error I got when trying to ssh was this
and is explained how to fix it that post, and this
sh: /usr/X11R6/bin/xauth: not found
which I still have it.
Also after dd command i got a "Bus error". Downloaded a new mmcblk0p1 by the way.
Sorry for the long post, I hope it makes sense and helps somebody.