I have to agree that plotting a force/draw curve would be the way to find out if your bow is stacking at the end of your draw. If we can take Tim Baker's word for it in The Bowyer's Bible 1, stacking is caused by string angle. A 64" bow at your draw should be long enough not to stack. But he also says that bows that bend too much at the tips increase string angle and therefore stack.
I'm glad you started this thread, because it makes me want to take the time to plot f/d curves on some of my wooden bows. Some stack more than others, even though they are all long enough for my 27" draw, at least on paper. I've noticed that I have a tendency to palm or torque the bow the last inch of draw. My accuracy improves if I grip mainly with my forefinger and thumb.
To answer you original question, a 45# bow should gain 2.25 pounds per inch of draw according to "Shooting the Stickbow". But I think that assumes a bow that has zero stack. If the bow is stacking, the weight increase for that final inch or two would have to be higher, probably by quite a bit.