I'm floored. Seriously floored. This is so many sorts of brilliant that I hope I remember them all.
First, the story. The STORY! Action-packed, full of wonderful characters (is Euro Floo compatible with T-Com, and if so, can I please have Magda's number so I can propose?) and politics and magical detail and EUROPE! I so love how you give us the grand tour of the Continent, showing us real places and real people where Rowling merely gives us daft caricatures. There is such a sense of place through your fantastic attention to detail (drawing our attention to Latin script in Bulgaria, for example, or the Wizarding Rough Guide), and I'm absolutely taken with your names and pseudonyms. David Yalçin (so much more than the mere name for which its bearer takes it), Albrecht Knochen (broken bones should be something he can relate to, with his profession), calling Thomas Riddle by his full name, not by the title he's given himself or an abbreviation, the anagrammatic Carole, and, of course, Herr Confidential (who is brilliant).
Also, the modernised magic, the terminology you use (Nundane/Muggle), and all the politics, oh my, the politics! Complex, believable (both on the side of the resistance and the Neo-Grindelwaldians), realistic, but still distinctly Harry Potter.
And then there's so much beautiful, descriptive, insightful and textured writing -- I'll just quote these two bits:
He did not consider the farm any less his own in light of the deception. On the contrary, he had come to discover that a stolen life was, in its way, more genuine than the fickle circumstances of fate and luck. He had also discovered that country living bred amateur philosophy.
He was considered new to the school in a way that the other first-years were not, but he was from the country, which forgave some sins of ignorance under the blessing of the folkish, romantic tales they read in their literature and history classes.