I may be reading your info wrong but I think you are making it harder than it is.
1 MOA = 1.047 inches per 100 yards, so each MOA click is .262 inches, assuming the scope is calibrated correctly.
1 IPHY = 1.0 inch per 100 yards, so each IPHY click is .25 inches, assuming the scope is calibrated correctly.
So if your turrets click adjustment moves .262 per click then it is actually moving what it should for true MOA.
So to test this you can either shoot to find drops or just measure the change in the reticle as you move your turrets. I prefer to just measure the movement as it saves me shooting ammo and keeps shooter error out of the equation. Set up your target, for me a tall piece of cardboard, at exactly 100 yds. Buy or print out 1/4 inch graph paper, make sure it measures true, and piece enough together to get 30 inches. You can buy it large enough but if I print it I have to piece it together. Mark your start point on the graph paper so you don't loose it and then dial in say 20 MOA. Then measure the distance your reticle moved. Then take that distance, divide it by the number of clicks, 80 in this example, and you have your true movement per click in inches. So if your reticle moved 21 inches you would have a click value of .2625 which is very close to true MOA. if it moved 20 inches it would be IPHY or .25 inch per click. If it moved 22.5 inches your click value would be .281.
If you want to shoot instead of measuring you simply shoot a base group then dial 20 MOA then measure the distance between the two groups, then divide that number by the number of clicks.
With some ballistic programs you can actually enter in the true correction per click that you just calculated get the program to read correctly, ie enter .262 or .25 or .281. Other programs want you to come up with a correction factor which requires you to find the error % and then enter that, ie .262 (true MOA) divided by .281(the actual click value you determined) = .929. Then your data card will show correct drops assuming other data is accurate.
Clear as mud?