That is indeed an incredible story. I don't think there are many pet owners out there that could have handled it was well as you did.
I am not a vet, or have any health related degree, but it is very fascinating to learn about these critter, and the diseases that inflict them, and specially how resilient and willful they can be. I am glad you were able to find such competent vets that would care for him like they did.
Thanks for sharing your story, I hope Petrie just continues on improving.
Wish you all the best of lucks!