This is going to be much easier than you think. It isn't actually a foia request.
Since you are the deceased veteran's next of kind you can go here: https://www.archives.gov/veterans/mi...ervice-records
and request his records.
I deal with veteran's records every day and have looked through literally thousands of OMPFS. The exact details of what you are looking for may not be in there, but you may be able to infer alot.
It is not uncommon for vet's service medals and awards to be incorrect on their DD-214, especially during the era when your dad served.
Dunno how much of the details you want to share in public, but if you'd like to chat about it some more, hit me up via PM.