I can tell you a little bit about the 64th. FA Bn.
It was activated 1 OCT 41 at Oahu, HI., and departed same date; at Guadacanal 23 DEC 42; at Russell Island JUL 43; at Vella Lavelle, S.P.,17 AUG 43; at New Zealand 9 NOV 43; at New Caldonia 24 FEB 44; at Philippines 11 JAN 45. at war's end at Bambam, Philippines AUG 45.
As member of 25th. Infantry Division participated in these campaigns:
6. Central Pacific 11.Guadacanal 14.Luzon 16.Northern Solomons
The 25th. INF DIV suffered the following casualties:
Killed in Action: 1,235 Wounded in Action : 4,190 Died of Wounds:262
You mention that your dad survived Pearl Harbor. I was 15 at that time, a sophomore in high school (R.L. Paschal, Fort Worth, TX).
I was drafted at 18, and served in the FA Training Center, Fort Sill, OK, for 19 months, then shipped over to become a Chief of Section, 985th. FA Bn., II Corps, Fifth Army through two campaigns in Italy.(31. North Apennines; 33. Po Valley).
I shipped out from Naples enroute home 19 FEB 46.
My reference for the above:
"WORLD WAR II ORDER of BATTLE" Shelby L. Stanton, Author Galahad Books, NYNY, Publisher
Hope this is of interest and helpful to you and your family.