Gender: boy
School:
School #21B
I believe this is the student who signed the book because the spelling is exactly the same, and the birthday fits perfectly. Also, his occupation was schueler, which means student!
I was able to find Harry's mother and brother because they shared the same addresses, transport date, and transport numbers.
Harry has a transport number associated with the date in his information, therefore it is safe to assume he was deported. Using the secondary sources, I found that daily deportations in March went to Chelmno, and all victims perished in the gas vans.