Not sure where to go with this now, except trying to confirm his birth date (and hope he gave the right details then!).
If we take on board that he stated his mother to be a Sarah Stewart/Stuart at the time he married and on his death reg, I don't think we have anything concrete so far

Dorrie, I can't access Royal Navy service records. Was the one you mentioned the only possible one? Nothing under the first name variant of Harry?
I wonder if there could be service records for Henry WW2? He was young enough (c. 39) to have been involved.
Monica