I'm personally mixed about ambiguous/open endings, but I really resonated with a lot of this! Especially what you said about stories existing inside a bigger story; I'd always thought of stories as glimpses into an alternate universe, and it doesn't stop just because we're not looking at it, you know?
I also agree with what you said about declarations of love; whenever the 'I love you' is treated as the final stop of a couple's journey it's always a bit disappointing. There are so many interesting aspects of being together that get glossed over in those cases :(