My father was also in 4th Marines, 2nd BN, E company. His name was William P. Dale and he was a 2nd Lt at the time of Okinawa. Unfortunately he just passed away 5 mos ago otherwise I am sure he could have been of great help as he had a remarkable memory of that period.

He was wounded 3 times on Okinawa with the worst being shot through the abdomen on 5/25 which put him out of commission for 2 mos before he was returned to duty as they took Tokyo Bay in August for the surrender.

Anyways, he has a huge file of his orders and paperwork relating to his time with E company. I am presently looking through it all to see if your father's name is mentioned in any of the orders.
I know that period you mentioned was a brutal time for company E losing many many men near Sugar Loaf Hill. My Dad talked about how they had to go into those tombs to clear out the Japanese who had dug into the hill.

If you haven't read it yet, there is a book by James Hallas entitled "The Killing Ground on Okinawa: The Battle for Sugar Loaf" which discusses that battle and the details. The 4th Marines lost a large number of men there.