I'm not 100% sure I've followed this properly - but isn't it inherent to playing a vampire PC in a Vampire RPG that one is playing a murderer?
V:tM vampires rarely kill when feeding. Usually, they have a "herd" they feed on who voluntarily offer their blood (because having your blood drunk by a vampire is apparently very pleasurable), or they use various mind whammies to make their victims forget they had their blood taken.
This is the chart for defeating foes by HD. One important thing to note here is you can't get XP for killing something without 'significant risk' to themselves. The GM has room to interpret what this means but the book says a 7th level character in need of one XP can't round up his friends and surround a single orc, expecting to get XP. And you don't have to kill the creature to get the XP, you just have to defeat it. The values below get much greater if a creature has good abilities. A mountain Loup Garou has 7 HD but is worth 4,000 in the Ravenloft monster section of the ROT boxed set.
As a first order of approximation, this is basically the same as the 1e table with averaged hp values (so in 1e, a 1-1 to 1 HD creature would be worth 10 XP + 1 XP/hp, but in 2e they just make it 15 XP). A little higher at higher levels, but not exceptionally so.
The difference that pumps the values up, particularly at higher levels, is that in 1e the table has additional XP values for each special and exceptional ability. So a 1 HD creature with something that counts as a special ability was worth an additional 4 XP, and something considered an exceptional ability an additional 35 XP (the difference between these two become proportionally less at higher levels, presumably because exceptional abilities become more common). In 2e, these instead counted as additional HD. Since the creature XP table has escalating numbers, something with multiple special/extraordinary abilities would be worth many more XP in 2e than in 1e.
For example, I think a ranged attack was considered a special ability. So a 1e 1 HD creature with a ranged attack would be worth 14 XP + 1 XP/HD, while it would be worth 35 XP (as a 2 HD creature) in 2e.
I should say I haven't been making heavy use of this (I've just been leveling the party at regular intervals because I am running them through an anthology adventure (and they need to be the right level to play each scenario).
IMO, milestone leveling probably doesn't work very well with 2e – or at least, it can cause weird effects. After all, XP was used to attempt to balance classes (as in "It's OK if a class is more powerful, we'll charge more XP to level up." It is debatable how well that worked.), and it's an integral part of how multiclassing works. If I was going to do story-based leveling, I'd do it via XP totals, not levels.
