How does Browning tell the story in Porphyria's Lover?

Browning uses a number of different narrative techniques to tell the story in Porphyria’s Lover.
The poem is written in first person, in past tense, from the perspective of our narrator who is unnamed but as the title suggests is “Porphyria’s Lover”. This means that the telling of events is not completely reliable and can be assumed to be biased. The narrator’s first line of speech, “I listened heart fit to break” suggests he is waiting for someone, maybe even longing.
Browning structured this poem as a dramatic monologue and has included structural features such as enjambment which makes the poem sound less like a crafted speech and more like a casual conversation, which may be seen as eerie considering the events later on in the poem. Porphyria’s Lover follows an iambic tetrameter in the first four lines, however in the fifth line “I listened with heart fit to break”, the regular tetrameter breaks, just like our narrator describes his heart breaking.
The poem is set in the lover’s cottage in a secluded forest in the middle of the night. The reclusiveness of the cottage may symbolise the fact that Porphyria sees her lover as a secret, less important part of her life and wants to hide him away. However Porphyria is not given a voice in the poem and does not say anything throughout possibly showing that the narrator sees her as his possession who does not have a voice of her own. When Porphyria enters the cottage she made the interior “blaze up, and all the cottage warm”, contrasting the description of the stormy weather outdoors. This sudden change in atmosphere gives the reader an idea of the narrator’s feelings towards his lover, and the effect she has on him.
Browning’s use of language also helps us to understand the mind of the narrator, from as soon as Porphyria enters the cottage the word “and” is repeated again and again, on almost every line up until he decides to kill her, from this it seems obvious that her lover is observing her every move, perhaps he’s watching because he’s in awe of her, or maybe it’s because he doesn’t want her to get away? “All night long we have not stirred, and yet God has not said a word”. This quotation has several connotations, firstly Porphyria’s lover may think that he has not been punished by God, his actions are justified and unquestionable or he may be feeling guilty, but again, by God not punishing him he has done the right thing for the right reasons.