Why does the position of the ocean ellipse change over the course of a given week?

The ocean's size is completely dependent on small changes within the gravity from the sun and moon. The distance to those bodies perpetually changes. The moon goes from nighest to far away distance in concerning twenty-eight days thus as a result the moon would be greatest (and it's nearer to the earth as well). The larger gravity would suggest that the ocean is a bit larger.

i would say

+15-35=-20

going in opposite directions