1) Point One: the day is divided into four. Only in the last quarter of the day, is Hashem enjoying (being “pleasured” by) what we do. This is the playing with Livyasan idea, we are all the fish in the sea one with Him maximally serving Him
Point Two: there are Souls called fish which are the highest Tzadikim, and there are Neshamos compared to the שור הבר that go into the three (or four) classes of צדיקים בינונים and רשעים. The Neshamos called לויתן raise the rest up לעתיד לבוא.
2) This battle only happens after Moshiach comes because only a גילוי העצמות ממש achieves this and this is only לעתיד לבוא. The לויתן raises up the lower Neshamos (שור הבר) and in doing so experiences an עלי’ה Himself.
