The OP provides good details about the overarching setting. I'm more curious about where the PCs are and what they'll be doing. So far the premise seems to be 'your character is seeking to join the Hellsingers' and getting trained. Where does this take place, since the Vatican is sealed? What are your plans / mission statement after that? It could be that people see signing up for and training with the Hellsingers as a less-than-enthralling plan of action.

One other thing that came to mind. As a rule of thumb, a good 25% or more of players who sign up for any RP will either never post or make one post and then disappear, so with a maximum of 3-4 players the entry toll would hit pretty hard. People also might not like competing for limited slots. Far be it from me to tell you how to run your RP, of course, so please don't take my rambling too seriously.