Philomel Cottage - other possible endings

I've been re-reading her short stories and this one's def the best when it comes to suspense. Oh my god. I was in awe after reading it, and because it's kinda vague and slightly open ended, I thought there could be multiple diffrent angles for this... like

1) Maybe he(the dead husband) was innocent and she was the killer - When it got too evident - eveything was pointing him to be the killer, i thought it's too easy for Agatha's stories and start thinking she(the narrator) was the killer but just delusional and justifying. Very unlikely, i know.

2) She did poison him and what she said about her past was all true - Easily explains why he died actually.

3) She didn't poision him but scared him to death.

I know 3) is mostly how people view/understand this ending. But again I thought this novel is briliant in a way there are possibility for 1) or 2). Thoughts?