While your post was an interesting mathematical exercise, the only way to establish its validity would be to evaluate it against real world results. The problem with such exercises is that they tend also to be only of heuristic value, an exercise in "what if" as it were.
You're absolutely right, and I've tried to be careful not to overstate the "validity" or concreteness of what basically amounts to a thought experiment. I've
proven nothing, really, with regard to calibers and bullet types, although at least somebody finally attempted to explain in numerical terms how certain isolated parameters such as bullet diameter can, in theory, affect the probability of effective wounding.
While I wouldn't put any real faith in the actual numbers generated by such a crude (I could refine it greatly in mathematical terms but that wouldn't make it any more valid), incomplete system of estimation, it at least gives us a sense of scale that can help guide our intuitions as to what type of ammunition we feel comfortable using. And let's face it--at the end of the day, the latter is really all we have regarding this whole subject.
Unfortunately, even the most scientifically rigorous studies have given us few if any answers that common sense couldn't have done, and don't often put a numerical value on the advantages of many parameters, save for minimum penetration. Even then we could make up our own minds, allowing our gut to tell us how much is needed to punch through some bad guy's potentially thick beer gut (many folks think that 12" is good enough, but it's really a bare minimum--the goal should be 18" as the FBI, for one, suggests as being "preferable" meaning advantageous).
The problem with this is that more often than not, "all else" isn't.
True, but I made sure that the most significant, known factors (feel free to bring up any contradicting ones) were on either side of the lower and upper bounds for comparisons. This means that whatever percentage is estimated when comparing JHP against FMJ is a lower bound because JHP bullets have a shape that is superior at wounding, particularly at the edge, while a comparison between two calibers in FMJ is an upper bound regarding round-nose bullets, which wound poorly beyond the tip (additionally, among the most common handgun calibers, smaller tends to be faster).
Though the 9mm "haters" won't like it, this is most likely true.
Honestly, I wouldn't have thought so to start out with, but after taking such a close look at the difference between these calibers and twiddling a few numbers to my own satisfaction, I have to say that the proponents of 9mm use in the military are probably right.
I had always had a knee-jerk reflexive response in favor of .45 ACP when forced to use FMJ, but it turns out that it's in all likelihood more advantageous in JHP than in FMJ, which seems to run counter to the "conventional wisdom."
As long as penetration is sufficient, that is. If it isn't, then I'm not even going to touch that comparison, at least for now.
Personally, I try to err on the side of penetration because without it there would be a lot of vital tissue out of reach in the lower abdomen, assuming an anterior shot. With FMJ, there is not much question of being able to reach the spine or aorta with such a shot, but JHP may suffer in performance with exceptionally large individuals. This is why I currently use a .40 S&W JHP round that expands like a 9mm but penetrates several inches more deeply, just in case.