It's good to know the boundaries between species, thanks for the info. I referred to silver as a weakness for vampires yes, but only in it's blessed state as that would technically turn it into a holy weapon, however as you've said that holy weapons do not affect vampires, that too is no longer an issue. I too found the OCD thing laughable, however that's the main reason I posted it in the first place. I figured however that blood deprivation would at least result in a weakening of the vampire, or at the very least some negative side effects akin to a junkie suddenly going cold turkey. 

Does the fatal bite rule apply between species? By which I mean if a lycan bit a vampire or vice versa, would the bite be fatal? Also, you stated that the vampires in this setting precede humanity, does that mean that humans are a result of a mutation in the species, or are they simply a result of parallel evolution? Sorry about my wordiness, I just find topics like this fascinating.