While your math is fairly correct, you sure made it hard on your self.
Do your self a favor and make it simple on your self. Use 1,000 sq ft as your test plot to find your Gallons per thousand. Most all pesticides application rates are listed as 1,000 sq ft or an acre.
At you present calibration your 25 gal tank should do approx 10,200 sq ft. Therefore by simply reading a Label you can multiply the per thousand rate times 10.2 to find how much pesticide to add to your 25 gallon tank. BTW .75 oz of 2,4-D per thousand X 10.2 = 7.65 oz which is close enough because of rounding error.
Now another suggestion would be to reduce your Carrier rate from 2.46 to ONE gallon per thousand by changing to a smaller tip. Most Herbicide with work better at a Higher AI (concentration) per gallon.
it is one thing to do a off label applications. It is total stupidity to post it on the world wide web and expect people to approve.
You can lead a Donkey to water but you can't make the Jackass Drink