6:The letter is preparing implicitly the reader for the absence of Elizabeth, in Victor case for her death, who is going farther away from who he loves, also expressed on Elizabeth Letter, she is concerned about Victor.
7: Victor Falling into illness is a reaction psychologically induced, he feels grief and guilt but is not facing it as he should. The mosnter is starting to create a relation with his creator but in a distorted way, he is making him feel the pain that the he (the monster) is enduring in solitude, he has become dehumanized and is filled with revenge, exhibited previosly by the mosnter, the Autor is writing also influenced by the romantic movement in late XVIII and beggining of XIX, emphasizing the experience of the nature with the feelings of her characters.
8:The frame structure help develop the plot, because is redundant in the sense of ownership, family, love, absence and revenge, this chapter is centered in the process of change from Victor, he has assumed the inhumanity of the monster that he created, now he found himself alone, as the beginning, but now life is literally, he used to had family and loved one that cared about him, but he didn´t appreciate or see, he has more fulfilled with the obsession of his creation that at the end, left him really alone. Both Victor and the creature are now aware that both had a living need.
The Frame used by Mary Shelley is a layered narrative, is developing a history inside another history, so it moves around time with natural flow and also allows the teller to direct the view of the readers as she wants, letting they know the characters in a more complex way.
9: Until Walton, the body of Victor and the creature are all together, Walton finally sees Victor in reality and the curse and fault that were with him, it also exposures the tension between the creature and his creator, but also understanding the human part of the creature and the mounstrous face of Victor after his uncontrolled ambition, Walton understand the history behind and walk away, letting the creature to go follow his fate as Victor.