I also second 'Coingrabber' staying outright. I also don't think that you need to throw a huge change into Ivy's name - if that's something you want to stick with, by all means stick to your guns. Even the alternative, changing it to something which might be shortened to Ivy would work if you wanted. No big thing. My Vampiress is definitely bordering on being a wish-list. In a setting where all of my Vampires are basically French, she's a Norse princess who was saved, seduced and 'wed' by my general - with the anglecized name 'Christobel' and she's just as capricious as Ivy in your story.
On that note, keeping that 'darkness in men's hearts' is something that makes Vampires believable and interesting. Sure, they might be heroic and well-intentioned, but there are plenty of heroes and do-gooders fighting for Order. The idea of becoming something as hideous as a Vampire means that there was some corner of your soul that wanted to go through with it. That's one of my favorite "modern additions" to Vampire lore - the idea that in order to become a Vampire, you have to volunteer willingly. It's not like a zombie or werewolf where a mere bite will turn you whether you like it or not - you have to actually consent to the change, whether it be through honesty or some form of deception.
You do a good job with that in the update. The idea that Aiden not only hates his rival enough to consider murdering him over a girl, but that he reaches a point where he is so desperate to live in order to carry out his revenge that he resorts to cannibalism to survive - that's showing the part of his psyche that is truly broken and twisted. That seed of evil that flowers into a full vampire.
On a side note - have you read 'The Count of Monte Cristo'? It's historical fiction, but could actually serve as a cool basis for your story, as it already follows very similar lines. Edmund Dantes starts off life as a merchant, doing a good job for himself. He's about to get married to the girl he loves, and set sail with a cargo that will set him up for a comfortable life. Jealous of his bride, his success, and his good luck, his friends conspire against him and have him accused for treason. He gets locked in prison. While there, an old and dying cell-mate teaches him everything he needs to be a respectable nobleman, tells him of an immense treasure, where to find it, and they actually conspire that when the man dies Edmund will take his place in the burial shroud and sneak out of what is basically Alcatraz. Edmund actually plans to be buried alive and dig his way out but is thrown into the sea instead. Once out, he locates the treasure and uses it to pose as the mysterious 'Count of Monte Cristo', traveling to Rome and then Paris to undo everyone who wronged him in life. Along the way, he also uses his wealth to aid those who had been kind to him.
During his travels, the Count seems to be all-knowing, and all powerful. This owes largely to the fact that he already knew these people as Edmund before they met him again as 'the Count', but also to his superior intellect and his ability to buy off nearly anyone to play a role in his schemes.
I loved the book, and it definitely has the makings of a pretty bad-ass Vampire story. Everything goes as you said - Aiden is doing well in life as a thief, and plans to marry Ivy. One of the thieves outs his actual identity as a revenge (bros before hoes, honor among theives, etc) and Aiden is cast out or imprisoned. While there, he learns of another prisoner/outcast, perhaps a man in an iron mask (another of Dumas's stories), who is a Vampire. Perhaps the Vampire is just a guard, or maybe even runs the prison and uses the prisoners as feeding stock (endless possibility here). Anyways, Aiden manages to convince the Vampire to turn him into Undead so that he can escape by feigning his death and digging himself out of his grave. Once out, he returns to look for Ivy. With the whole 'Incurable Disease' thing, maybe Aiden initially poses as a physician with a cure. He offers the cure (vampirism) to Ivy, who accepts. Using his daughter's health as a means to extort her father, Aiden and Ivy come into possession of all or most of his wealth, and then go on the road, traveling from town to town to hunt down the members of the Black Crow, which has now become a very successful (and possibly misguided) guild in his absence and embedded itself in every major city and town throughout the region. Obviously, the men who sold Aiden out are the ones at the top of the ladder, and the ones that he is working his way towards killing.
Seriously, I could write this whole damn thing out for you right now. Possibly whether you ask me to or not