First, 6% bf is about right for a speedy strong safety.
Second, what kind of sprint traing are you doing? Overspeed and resistance, how is your reaction time? From your numbers and bodyweight/comp it seems you may already be strong enough and explosive enough to be running faster times than you are. You will get faster if you lean up gradually, might not need to say this.
Timing of your last true meal of the day can make a difference in bf %. No meals after 7pm is a good standard to follow assuming that you do not work an evening or night job. Loading up on broccoli or lettuce with your last meal instead of other carbs will help too.
Replacing some of your higher glycemic type carb intake with lower glycemic type carbs throughout the day should help as well. I am a huge fan of chickpeas. Remember that you will need adequate calories to keep up your strength and energy but as you get much leaner "some" of your strength may initially be sacrificed. It will come back when your body has a chance to acclimate to it's altered shell, however in your case the football season may hinder your strength gains anyway so I wouldnt worry too much if the power drops a little.
Are you positive that you are at 11-12% bf? you look a little leaner than that.
The first ten yards of the 40 yd is what makes or breaks you. Starts and reaction time are possible areas of focus for you to work on if you are not already. Do you train with people who run in the 4.4 range? I assume yes but training with them may help your time drop too especially in chase drills, you chase them they chase you.