The Deutsches Dienstelle WaSt in Berlin will have records of his service:
As a relative you will be able to obtain them if they have anything.
The award of the EKi or EKii is not unusual but unless you have his Soldbuch it will be almost impossible to trace, unless it comes up in the records. They should at least give you an idea of which unit he was in. From there you can perhaps begin to research his movements.