Wow, Ludi, holy cow! You should be very proud! I can imagine all the nay-sayers and your own doubts you had in the midst of all that work!! But good for you, you hung in there! 18" down to take out rocks??? Man, you are devoted!! I've been studying that rocks actually attract electricity from lightning and the roots actually like it, so some rocks are helpful, so maybe you can have a break now!
I tried the above-ground hugelkulture with dirt mounded over it and it failed utterly because the voles and mice dug into it, made air tunnels out of it, built their condominiums in it and their population doubled. Then taking it apart again was awful. So I know it is hard to know just how far to take some of these methods we read about.
Great pictures, and what a lovely garden you are building!
"Life flows on within you and without you"...George Harrison
Coastal California, USA, Mediterranean climate - no summer rain, a little frost mid-winter