Re: helgoland church books
According to my notes on what church records are available, a baptism book from 1795-1837 exists.
I also checked my three address directories of Helgoland and did not see the name Spitzenberg.Also, checked a set of books on Helgoland laws, but, saw no such name.
I understand many people got married on Helgoland just for the fun of it.Maybe they had their babies there, too, sometimes.It was already a time when people came to the island to vacation.
I would suggest, since you have your great grandfather's exact birthdate, you write to the Nikolaikirche, 27498 Helgoland, Germany.Since the island was under British rule for along time, English is probably okay.