How about an Epicure of Blood

Although Thoughtseize and Inquisition of Kozilek are some powerful cards in modern environment there is no further structure to support this mechanic in your deck. You don't really profit from them (like other modern decks can). If you want to play vampires I think you have to focus more on speed and dealing your damage quickly (+1 Lightning Bolt ). By the time you can use Bloodline Keeper properly you're most likely already overrun. Aim for a solid output of creatures and try to replenish your hand if possible with your sideboard Night's Whisper

Good luck with you build. +1

Hello! I would definitely consider putting in Gifted Aetherborn. It's a really powerful card that you can put out early in the game for some initial defense. Also, Indulgent Aristocrat is another good card that you can put out early, and then you can later start sacrificing Bloodline Keeper  ^Flip's vampire tokens to beef up your other vampires. OR, another good combo with Indulgent Aristocrat is to throw out a Dark Salvation, which could give you a bunch of zombies, and then sacrifice some of those zombies to beef up your other vampires with Indulgent Aristocrat. I think if you take out some of your higher CMC creatures and put in some of these to give yourself a better defense in the beginning it will make this deck stronger. Unless you have a good defense at the start or unless you do some control mechanics, you might not get the chance to even put out higher CMC cards. I hope this helps!

Oh! Drana, Liberator of Malakir and Mirri the Cursed are also a pretty sweet cards. I might even consider just making this a mono black vampire deck!

You're off to a great start by having answers like Fatal Push and Lightning Bolt mainboard and not just throwing in every vampire you can find. I definitely recommend taking a look at your curve - 2.38 CMC is pretty high for Modern that isnt a control or combo deck so you probably want to tone down the 4 drops and add more 2 drops to try and get on curve as much as possible. I recommend either Shattering Spree or Vandalblast for anti-artifact hate (Ensnaring Bridge is always to be considered). Dismember and Ratchet Bomb should be considered as well. Maybe even Grafdigger's Cage, Nihil Spellbomb for the sideboard. Gifted Aetherborn is a fantastic suggestion, as far as other vampires you seem to have nailed most of the ones im familiar with so you might consider some more creatures that arent vampires even if they dont directly synergize, for utilities sake.