I think that Lejb Hauser is Icek Labj Hauser, because that is the only person it can be. If you go to the names under H, and then go to page 4 of all the H surnames, you will see that there is only one Hauser, and only three male Hauzers. When you search the database, there is only one Hauser with with anything similar to the name Lejb, and that is Icek Lajb Hauser, whose birth year (1927) corresponds perfectly with the school Lejb H. went to (1926-1931). Even when you change the last name settings to "Fuzzy", there are no other Lejbs or Lajbs. I even searched through all 46 Hauzers and all 86 Hausers for corresponding ages.
Lajb and Lejb are very similar. It also makes sense that a boy of 14 years would abreviate his name to Lejb, which is a variation of the Yiddish name (Leyb) for lion, or "Judah", (compare "Sonya which is Russian, to "Sonja", which is polish). The name Icek was probably an overly common name (the name of a great Jewish patriarch) and simply means "laugh" or "he laughed" in Hebrew.