2. Vampire tavern keepers can serve other vampires booze without any significant risk of being fed upon (I think: I don't know if vampires take advantage of vampires unconscious due to inebriation to feed upon them). You can also use goblin tavern keepers, as goblins don't sleep. There's no way to get them to eat, though (and even if blood counted as food, it won't be in their preferred list).
3. Screening of migrants and isolation and observation of those not shown to be alive. That's not particularly efficient, though, so vampire hunts tend to start when someone has been found drained. Also note that visitors (including those hiding in performance troupes) can be vampires, so blocking visitors would block that threat, but it's probably at too high a price (regular visitors are currently announced as being vampires on map entry [although it's easy to miss it in the log deluge, but performance troupe members are not]).
5. DFHacking could probably do it. The vanilla method is to find a deity that curses defiles and get your gobbo to perform such an act. That probably involves having the bugger get stressed enough to start tantruming while inside a suitable temple with statues. I assume it would be tricky to recover the sanity of the resulting vampire (or were) , though, so you'd probably end up with insane vampires.