An Allusion or Insanity?

As explained already by others, there are clearly references to historical events in the story. This is what examining narratives from the view of New Historicism is all about! However, to what degree can we say that Stoker really intended there to be a connection? For example, in my interest and research online, I stumbled upon the thought that Dracula may have in part been modeled after the countess Elizabeth Bathory of Hungary who is famous for murdering hundreds of women in order to bathe in their blood to look more youthful. This is why, some propose, Dracula looked younger after feeding on the blood of his victims. Although one may think this is far fetched, it may not be all that out of line. At what point may we say that a particular scene or characteristic is an allusion to a historical event while another is just too unbelievable to really have a connection? I would be interested in hearing your thoughts.