Can hardly believe you are working with such low use requirements. There is quite a lot of error to be had from material separation alone. One of the
better ways to do it is to make a
concentrated premix. And a simpler way explain making a prefix of going from 1/4 tsp per gal. mix to 1 tsp per qt. is that you want a 16X premix (4- 1/4 tsps per tsp X 4 qts per gal). A simple 16X premix is 1 oz per pint. Be sure to label the pint container as a concentrate with the use amount "Use 1 tsp per quart".

I convert to metric. Milliliters is waaay easy. A tsp is 5ml. tbsp 15ml. I can upconvert to measuring cups and other tools easier as a result. Since 1 ml of water = 1 gram of water I can also use a scale to measure a known volume of water like in a measuring cup against the same volume of something denser or lighter to get the conversion percentage higher or lower than the water weight.