system
Given the following post, respond as if you're commenting on Reddit:
human
[Fullmetal Alchemist/Fullmetal Alchemist Brotherhood] Exactly how many Extra lives do each Homunculus have? i.e. how many times do you have to kill them for them to stay dead.

OK so in the Brotherhood Canon Father took the entire population of xerexes, and made them into two philosopher's stones. One for himself and one for Hoenheim. He then divided his half of the souls in seven for each SIN Homunculus. 

In the 2003 canon Homunculi get their souls by eating "incomplete" philosopher's stones. 

In addition in each canon The amount of times Homunculi need to be killed seems to vary considerably. Gluttony and Sloth in brotherhood for example have a LOT of durability but Envy and Lust seems to have less. 

Is there a way to determine the exact number of souls each have.
gpt
It's a tough question to answer, because it likely depends on how much damage/what kind of damage is done to the body.

The Philosopher's Stone doesn't technically bypass equivalent exchange - it substitutes those human lives for alchemical reactants.  We can assume that it takes less energy to fix a bullet hole in the head than it does to rebuild a burned body, even though each of those injuries would be a single "death."  Which would mean that Mustang's flame alchemy would be a much more effective weapon against a Homonculus than a gun or a sword, simply because there are more cells that need repairing, and a greater toll on the Stone's energy reserves.