Okay, so the easiest thing to examine here is the means of death. Given how it's described in-story, and with a couple more assumptions, it's arguably similar to Leukemia, except it's red blood cells instead of white blood cells, and it isn't exactly cancerous. Let's call the cause of death... Erythremia (which is mildly amusing to me because that pretty much just means "Red Blood"). Moreover, instead of the main risk factor being malfunctional Leukocyte buildup, it is the resource strain from Erythrocyte overproduction. Now, based on my knowledge of biology, this should be able to be countered by supplementing one's diet, but would probably become untenable after a certain point. The reason for that is simple: as the condition progresses, the blood production (allegedly, at least) also increases. This is probably the result of the vampire's bite containing enzymes that upregulate the division of Erythroid Progenitor Cells (the text suggests genetic alterations to the EPCs themselves, but that's much more difficult and fanciful). Evolutionarily speaking (assuming vampires have something resembling reproduction -- the chrysalis thing doesn't count), this probably developed as a way to reduce the chances of a bride dying as a result of a long feeding sessions, reducing bridal death rates to something more manageable and sustainable. Of course, the simpler & safer solution to that issue is for the bite itself to contain division factors, but biology isn't obligated to constantly be that elegant.
Next, let's look at the pheromones secreted by a bride. Given the whole fever incident, we know that these pheromones are likely secreted as part of sweat. Theoretically, these pheromones, or at least a precursor, could be produced by the vampire and secreted by their bite. They would then travel through the bloodstream before collecting by sweat glands (not in them, obviously, because that'd probably lead to horrible acne. The Vampire naturally has receptors keyed to that pheromone, with each vampire being associated with a marginally different one. In terms of evolution, this obviously helps a Vampire identify and locate a bride when needed, in addition to pushing them to feed, as biology is wont to do. This, I feel, is the second most elegant mechanism of a vampire's function: Pheromone secretion would theoretically be mostly dependent on the Bride and how much she sweats, and since the vampire would ideally be able to pick up that pheromone even at extremely low concentrations, it shouldn't run out before the Bride is bitten once again. Most potential issues with pheromone/precursor buildup could be easily solved by having it degrade after a day.
Now, for the whole "withdrawal" thing. First, I'd like to correct something: based on what we can observe of Sara's behavior, in addition to common sense regarding the development of physical dependencies, this is probably not the result of withdrawal. Rather, I feel that this is the result of something far more insidious: Venom. Or rather, a precursor that develops into venom after around 24 hours. This makes it so that daily feeding is 100% necessary, from the moment a bride is first fed upon to the moment she dies. Naturally, the bite also comes with an enzyme that degrades the venom, but degrades before the precursor develops into venom. As one can no doubt surmise, this makes it so that once a vampire takes a bride, the bride will have to become a blood bank, regardless of her will. Whatever the venom's exact function may be, I don't think we have enough info. I could imagine this originally developing as an antivenom thing, actually, where a vampire could cure a bride of something by taking them, but the venom precursor found its way into the mix to ensure daily feedings. Regardless, I'd say it is an incredibly elegant system, despite its morbidity. (On the vampire side, it's probably just the body telling the brain that it's hungry, in a rather brutal manner).
The fact that a vampire's saliva is anesthetic, and their bite is stimulating, I can assume that any of you could figure out the reason. As for the flower mark thing, I actually initially thought that it was some sort of artificial gland constructed upon the first bite, but that seemed... unrealistic. I also cannot figure out an actual biological reason for it, which is... fun.
Anyhow, assuming my theories are correct, the two main ways to save a bride would be to isolate the venom-degrading enzyme, and give it to them without the rest of the biological cocktail. effectively freeing them from their mate, or giving the bride regular bone marrow transplants to reset the Erythremia clock, as it were.