For such an unusual premise (and fascinating weaving of canon into AR), you had me hooked. Being mostly agnostic myself, I'll admit to not knowing about the Catholic rites, but you covered them pretty well and I wasn't as lost as I'd expected to be.
The genealogy you used here, though, was just wow. OK, I know I get a funny little bump in my chest when I read about Bram Stoker after having gone to the Stoker museum in Dublin, but for you to find a way to link Harry and Lucius and Voldemort and Grindlewald and Dumbledore... I just stand sit in awe.
And this: "Sodomy," I say bluntly. "Seven counts--" I catch myself, considering. "No, eight. Harry woke me up last night around half-four." was brilliant. Found myself giggling.
All in all, a wonderful fic even if you are on the other team.