Can I prevent cardiac arrest and fat transferring itself into the blood? I want a BBL procedure.

The pathologist is correct in stating that this is the risk of fat transfer, which is part of the BBL.  It is possible to get a fatal pulmonary embolus or a fat embolus.  It is also possible to have lidocaine toxicity or puncture an internal organ.  The risk of all of these is much less than 1% if you are healthy.
For your own safety, the board certified plastic surgeon you select should know everything about your past medical and surgical history and be able to make a determination about what labs should be ordered, the need for EKG, the need for medical clearance, the need for anticoagulation, the appropriateness of the surgical intervention based upon the risk factors and current physique, etc. The day of surgery, a hemoglobin, glucose, and pregnancy test are performed. 
Kenneth Hughes, MD, Board Certified Plastic Surgeon

Fat embolus is a very serious and known complication of fat transfer (which has been recently spotlighted in the media). While it is true, injection of donor fat into the infra-muscular plane (within the muscle) increases fat viability this does come with a significant increase in risk. There are large vessels deep to and within the muscle which can be inadvertently injected while grafting leading to a fat embolus. The consequences of such a complication are very serious and life threatening.
At the recent American Society of Plastic Surgeons Hot Topics (2016), data from AAAASF (ambulatory surgical certifying body) was presented, suggesting that BBL/gluteal lipoaugmentation demonstrates a dramatically higher risk profile than other surgeries. The Aesthetic Surgery and Educational and Research Fund is convening a task force as well. The hope is that we will have more concrete guidelines for addressing these very serious complications.
That being said, the safest way to avoid fat emboli is to stay in the subcutaneous plane (at the expense of fat viability)and avoid the deeper muscular plane. If grafting of the deep plane is planned, surgeons should consider blunt cannulas, aspiration prior to injection. Using a supra-gluteal approach to minimize the risk of inadvertent intravascular injection has also been proposed. While this will likely impact graft viability negatively, it will also lower the risk of a serious complication.
With regards to your specific question, according to AAASF data the risk of death from BBL will range from 1:3000 to 1:6000 (subcutaneous grafting will reduce this risk relative to intramuscular grafting). By comparison the risk of fatal complication from abdominoplasty is 1:13,000. 
In summary, the procedure can be safely performed, however, they should be performed by a board certified (ABPS) plastic surgeon with experience. These risks should be discussed as well as the strategies being employed to avoid them.

Avoiding deep injections into the gluteal veins is critical to avoiding the complication of fat embolus.Watch this brief video for more information.Best wishes,Dr.Bruno