As a matter of fact yes.
Just as an excess of iron is a debilitating condition in a living person, vampires too can suffer from the condition. I have know certain vampires to become very irritable and discomforted by 'what is probably' just that.
They are however able to self-regulate the excess by excreting it from their pores (sweating). A vampire can recover from such an imbalance in a matter of days.
There are 16 known oxides and oxyhydroxides of iron and a 'sweating' vampire can express a few of these, although only one at a time. I know of only five such expressions (not first hand, from records kept by the vampires themselves). Such sweat can therefore be either black, green, orange, red, (or even gold if accompanying with Sulfur poisoning.)
no
Since vampires do not exist, they have no effect on the Catholic Church.
with some vampires it doesn't affect them but with the ones it does i shouldn't think so. They were humans after all.
No, because vampires do not exist. You cannot affect anything that does not exist. But that said, it was indeed believed that the holy powers of silver would be extra-damaging to vampires, which were unholy.
There are fictional depictions of vampires with mental disabilities, but in reality, mental disabilities do not affect one's ability to be a vampire. Vampires are typically portrayed as powerful beings with supernatural abilities, regardless of any mental impairments.
No vampires tend to keep a normal lifestyle and tend to not bring up situations that could possibly expose them for what they really are.
The pH is not affected by iron (Fe).
First, vampires don't exist, but if they did, a whip would not kill them. Iron, silver, fire, sunlight, running water are the only things that are supposed to work.
It would depend on what the author of the fictional story wanted
No, caffeine directly affect the absorption of iron. It is the polyphenol compounds in coffee and tea that negatively affect iron absorption. Drinks containing polyphenol compounds should be avoided at least an hour prior to, and and hour after taking iron supplements or eating foods that contain iron to ensure they do not interfere with iron absorption.
The notion of silver harming vampires comes from Marvel Comics. From there, it made it's way into popular culture in movies and television. Silver does not affect vampires in the folklore. It doesn't even harm werewolves either for that matter. The use of silver as a weapon against monsters began with the Wolfman film of the early 1940's. Sunlight does not traditionally harm vampires either. That began with Nosferatu (the 1922 silent film).
Pepper spray typically affects living organisms through irritation of the eyes, nose, and respiratory system. Since vampires are considered undead, they lack these biological systems that pepper spray can affect. Therefore, pepper spray would not have an impact on vampires.