Probably start with the 2% solution.
Spray that out and calculate how many square feet that has been covered.
Adjust as needed.
10 gallon per acre is also a consideration.
So 5 gallon could cover 1/2 acre.
So 2 pints in 5 gallons could also be a start.
I seriously doubt that you can actually cover 1/2 acre with the 5 gallon in a spot sprayer.