I can't help too much but I can tell you what I've learned from my own geneology records (also German). I'm not sure what year yours are from or what language they were written in, but I can tell you spelling wasn't as standardized as it is today. I can't say I've ever seen Elisabethae or Frederici in my family records though I have seen Elisabetha and Frederick. Also, some records, like church records, were written in Latin and Latin variations were used. A lot of early geneology is researched from church records since churches were one of the few places that kept pretty good tabs on people. For example my great-grandmother's name is Lenore but some records show Leonora and even Eleanora.