If My Dog Killed A Rabbit Should I Be Worried That He Will Crave The Blood?

You should always be a little bit careful if your dog has killed or not. This will not necessarily make him any more or less dangerous than before. You will find that if you were feeding him tin food before a large portion of this was bunny meat. I always stress caution first, but I would not  be too worried he will turn into some blood thirsty monster.
We need to remember that a dog is a natural hunter,  BUT he is still your little earth angel, you just got to see a side of him you probably wished you didn't.
Its important that you remain as calm around him as you always were.

You might like to consider having him wear a muzzle him on walks, and use a head halter for better control, cats and bunnies might excite him. Typically its the chase and catch that he enjoyed the most. I wouldn't encourage little kids to run on in front of him, lol, but without knowing your dog personally I would be hesitant to make any guarantees,
BUT even with dogs that I do know very well I still do not guarantee any one thing or another, I guess its The same with us two legged kinds.