[Renate]

Yeah, it's a hassle, you can't go to EDL from fastboot.
You can get there from system/recovery with ADB.
There is this USB cable thing (that I've never gotten to work).
There are the test points inside, but that requires you to open the device.
(Unless you planned for this like I did and put a magnetic switch inside.)
There is the "nuclear" option, but I wouldn't do that without a copy of xbl.

In your shoes I'd probably just flash recmode to recovery.
But that's presuming that if there is a problem you can use EDL to wipe the start of misc.
Misc is not really a problem since misc-rec is 512 bytes that are supposed to be zero anyway.
I'd still cross my fingers though.

Ok, here's another thought. This is a boot image that I had when I was helping someone (who?) with their NA2. Since the boot partition is already trashed by you you can try flashing this. If it works, then you can get to EDL (maybe) and backup recovery.

Um, you have been flashing the correct boot_a/b partition?
This came out of b, but flash it to your active boot partition.