OK, that's aggregate data gathered from players. There's always a chance they might change it (for the worse) in the version you're playing.
Yes, Serum X counts as one drop, which are dropped by vampires, and there will be two lesser vampires that will drop Serum III on the final map 'Dark Resident'.
They changed the rules for how paralysis works in the Japanese version since the original Vampire Bride event. During the original event, vampires and lesser vampires had to deliver a certain number of blows and your unit became paralysed for a certain period of time (lesser vampires had to deliver 6 blows, whereas vampires had to deliver 4 or something back then). The big difference is that you could still use your skills while you're paralysed during the original event, but they changed it so that all skills—except the Prince's—deactivates and are unable to be activated while paralysed nowadays. This is a big deal because people were tactically using battle masters with the Strengthen Defence skill and units with the Recovery skill (e.g. Mischa and Crissa) to tank the vampires. With the revamped system, you need to use evasion units to deal with them effectively.
