OK, now throw a .357 mag - 125 JHP @ 1400 ft/sec into your equation. You get something considerably lower than the .45 ACP, but that round has probably accounted for more one-shot stops than the .45 in police service.
Interesting and fun intellectual exercise (and I'm a numbers guy myself, with a 4th-order polynomial describing my gas mileage), but probably not real useful.
To round out your background knowledge, you might research the Thompson-LaGarde study from 1904, the Hatcher "Relative Stopping Power Index", and the more contemporary Marshal & Sanow work on handgun stopping power, plus the Fackler rebuttal in the Int'l Wound Ballistics Assoc files.
Can you refer me to the FBI data you found?