But for all of your 20 years of hunting you have studied paper logic, and applied principles of bullets through game.
While I will not argue the fact that most high velocity rounds will totally turn the innards of critters into mush, a cast bullet moving along at a modest velocity will reliably drop game as will a modestly moving 45 caliber bullet like the Gold Dot.
You seem to be fairly knowledgeable, but you also seem to lack the experience with handgun rounds with which I have plenty of. I have been putting lead through critters since I was 6, and am now pushing hard on 48. I have read literally tons of printed info and have been where you are, but during this time I also had folks form the slow moving camp who helped me to understand that velocity isn't all it's cracked up to be.
I can't even begin to count the testing I have done with this that or the other loads only to find out that hey something else is going on here. Case in point. I have a .308 with only a 16.5" barrel. Using the factory Remington 150gr CL I get just a tad over 2500fps from it. this said, and by your calculations, these would be a pretty piss pour preforming bullet at 400yds. According to my Exbal program and drop test preformed by me to confirm, the velocity at 400yds is roughly 1550fps for an energy ftlb of only 801. However I have reliably dropped feral hogs at this and further ranges with it getting complete pass throughs, and plenty of internal damage telling me that the written figures are just that.
I will also argue that the 45 ACP slug put through the lungs of a deer will not close up much if any, and the resulting damage will put them on the ground. While maybe not quite in the explosive fashion of a HV rifle round it will be effective.
I have hunted feral hogs with a Ruger BH in 30 Carbine, up through my 454, and several auto's thrown in for good measure. I can tell you that they are much harder to put on the ground with one shot than any deer I have ever shot. This said the 45 has done a admirable job when I did my part, as did the Carbine, the 10mm, and the 38 SPL. None of these used HV explosive rounds.
So while the 45 ACP might not be the "best" choice which the OP already admitted to, and I agree, it WILL do the job if used within it's limitations, with good ammo.
Feel free to look through all of the albums at the links under my sig. You will see plenty of proof that a slow bullet will put game on the ground. There's a few big hogs with me and my little .308. The one in the back hoe bucket was a 385yd one shot DRT. The one with my grandson standing next to me with his toy rifle was a 450yds shot DRT. There are quite a few on a trailer and 4wheeler of which several were dropped with one shot from my 10mm using 180gr GDs.
If you really feel compelled to learn about how well slow moving bullets work, look up Veral Smith at LBT bullets and give him a ring. He can put it into perspective for you.