I loved reading your story, because everyone makes these (and other) mistakes. We all learn, and there is no shame in paying our "tuition" with working backwards. What I especially like is how you are combining the functions a feature (such as a big hole in the ground) could serve: a root-cellar, a greenhouse, access to the septic tank. Permies call this "stacking functions", something I should address in one of my upcoming posts.
Oh, I will look forward to that.
In reality the greenhouse has been battered each winter by the wind and the weight of the snow. We have reinforced it over and over and replaced the top but it is hanging agape now because the door zipper failed and the company doesn't make the ends with the door anymore.
I used it this spring for the transplants of our seedlings and the chicken just walked right in and pecked them to death. Another failed idea.
But we keep trying and improvising.