It's interesting - I just read The Metamorphosis last week. I still haven't really come to terms with it. It's a book that can bear many interpretations; certainly, there's much merit in the ones you present. I have to say, though, I didn't feel the desire to interpret the book. For me, it was more a question of experiencing the that level of pain - not only from Gregor, but from his family, too.
I'm not sure that I see the family or Grete as negative - though I know that's a pretty unusual reading. My sense is that they really did do the best they could do with an impossible situation for a period of time. If Grete snapped at the end, well, she's just human. When she mentions how thin she was, I thought there was a return of her compassion. And if the family seemed cold in their relief that it was over? Again, they were just human. They'd said goodbye to Gregor awhile ago - after all, they didn't know that he could still think or understand their speech. To me, the book is like listening to really heart-breaking Blues; I focused more on the feelings, the despair, than the meanings. I'm not saying those meanings aren't there - they just aren't what hit me when I re-read the book.
RE: Metamorphosis [By Franz Kafka] Review and Analysis ESP/ENG