How many ATP molecules are formed?
Sorry for the poor quality of the image, but its just as a reference for my answer.

You have made the question too complex. From the figure, we find that 1 H2O gives 2 H+ and 2 e-. 2 e-, through quinone cycle, provide 4 H+ i.e. total 6 H+ which form 6/3 = 2 ATP i.e.

1 H2O => 6 H+ => 2 ATP

Multiply this equation by 8 and you get:

8 H2O => 48 H+ => 16 ATP

So, 16 ATP should be the answer.

Reference:

Pradeep's: A textbook of Biology for Class XI, 2015, Vol. II, page IV/106