billy,
Since the water was given as a volume measurement, I converted it to weight on the basis of 1 c. = 8.35 oz., which is the standard conversion factor (although many people use 8 oz. as a rough number). A gallon and a half of water (24 c.) weighs 200.4 oz. Adding that to the weights of all of the other ingredients, I get a total of 638.4 oz. Since the 4 dough balls weigh 96 oz., that comes to about 15% of the basic dough batch weight (96/638.4 = approx. 15%). If you add the 96 oz. to the total dough batch weight, or 734.4 oz., the four dough balls represent a little over 13% of that figure (96/734.4 = approx. 13%). Of course, the relevant number is the 638.4 oz. number since four new dough balls are removed from the 734.4 oz. dough batch weight to be put in the overnight bucket to ferment.
Since the four dough balls are taken from a basic dough batch, they should initially have the same baker’s percents as the basic dough batch. Once you add the four dough balls to the next dough batch, there shouldn’t be much change in the baker’s percents except to the extent that there may have been some depletion of yeast and sugar because of the fermentation of the sour dough batch. There may be some loss of water along the way through evaporation of water in the sour dough batch, but I don’t think that it will move the hydration needle of the final formula in a material way. You will perhaps lose more from the water that sticks to the walls of the water container when emptying the water out of it into the mixer bowl.
You are correct that the actual percent of oil is higher than the nominal formula oil because of brushing the dough balls with oil. However, if the difference is 7% (of the formula flour), that comes to 28 oz. of oil, which is about 3.64 c. of vegetable (soybean) oil. I don’t recall that jokergerm specified a dough ball weight, but if we assume that it is, say, 15 oz., then that would be about 42 dough balls. I don’t think you would use 3.64 cups of oil to brush that number of dough balls. It is possible to apportion the formula oil between the oil used in the dough and the oil used to brush the dough balls, but no one does that sort of thing that I am aware of.