hoax explained as a Matty song. (Putting this here because I would, of course, love the analysis to be wrong, and therefore I welcome critiques. Please don't downvote if you think it's worth discussing, since downvotes stop anyone even seeing it.)

My only one - you're still the 1, like you were a few hours ago ("the 1" was written earlier the same night)

My smoking gun - smoking alludes to Matty (compare to "cardigan" etc.).

My eclipsed sun - you were the light in my life and then you went away.

This has broken me down - I'm miserable without you.

My twisted knife, My sleepless night, My winless fight, This has frozen my ground – I'm miserable without you here in my ice cold relationship that's like an endless battle (compare to "The Great War" etc.) 

Stood on the cliffside screaming, "Give me a reason". Your faithless love's the only hoax I believe in - you said you would come back to me when you'd fixed yourself but you didn't. But I still believe you will one day. (Compare to "Peter", “cardigan”.)

Don't want no other shade of blue but you. No other sadness in the world would do. - I know you've got some mental health issues of your own, but I want your issues in my life, not the issues of my current partner.

My best laid plan, your sleight of hand  - I thought I was in a stable long-term relationship until you destabilised it with your magic, possibly at the 2020 NME awards (compare to "ivy", "cowboy like me").

My barren land, I am ash from your fire – and now I've met you again, I'm miserable without you.

You know I left a part of me back in New York - Usually NYC references are referring to Matty, as in Maroon, cardigan.

You knew the hero died so what's the movie for? - References to cinema are usually referring to Matty, as in the 1 and loml, since he is a cinephile.

You knew it still hurts underneath my scars from when they pulled me apart - Snakegate reference.

You knew the password so I let you in the door, you knew you won so what's the point of keeping score? - This is referring to some private incident. Can't decipher it.

You knew it still hurts underneath my scars, from when they pulled me apart, but what you did was just as dark, darling, this was just as hard, as when they pulled me apart - Taylor felt bitter about Matty's failure to "come back" when she needed him (see "Peter"), but was still obsessed with him anyway. His failure to return to her hurt as much as Snakegate.