in order
-depends on the Vampire, on average I would say around twice as strong, but some older ones can dodge bullets. For reference, some werewolves can dodge bullets, but are on average four times stronger than a human
-yes, but most magic users have very strong willpower and can get around it

-depends on practice. The more you practice magic, the more energy is available to use. Creating energy/mass is always going to take more energy than any other process. First starting out creating a simple fireball the size of a baseball would cause a beginner to pass out, an experienced user may be able to do about four to five times that and be fine.
-depends how long they want to. Extending age with magic is very easy, but there is a hard cap at 100 years when magic starts to fade away and they will have a normal lifespan left.