Hey Nick.

I think “…perfectionist…” is superfluous it isn’t quite a flaw when considering the MC as a vampire and it dos’nt seam to add to his difficulty in getting over the obstacle. Perhaps consider an adjective that would necessarily create a conflict in our minds between him trying to do something and the way he is, for example: over ambitious, desperate, timid, anxious, etc…

Good call changing killing to death but maybe best to use this event to the maximum potential it presents could use it to set up an antagonist that caused the death of the master.

As for the ticking time bomb, the idea of a time limit isn’t inherent from the situation and needs clarification. If it is critical to the story then it dosn’t come across as such in the logline.

Also not sure that the part about the brother holds any clear relation to the rest of the story at this stage. If this is a B plot perhaps it shouldn’t be in the logline or needs to be re worked in to better serve the logline and story.

My try:
When his master is killed by a rivaling head-vampire, an anxious vampire servant has 48 hours to steal blood from a mobile blood bank to grow strong enough to defend him self and his brother from meeting the same fate.

Hope this helps.