A few things to point out –
This is more a horror movie than a crime drama or noir. It’s far more terrifying than slasher flics.
This is a fascist movie. There is zero forgiveness from any character for any character or any action. In this movie the “final solution” is always (another) murder.
The main character is not a “hero” as the movie would have us believe. He’s saved the physical form of the woman he supposedly loves but sure as hell not saved her overall well being after what he’s helped put her through. A woman is not just a body.
Also, the woman is not “innocent” but passively ignorant to a pathological degree.
As far as bad choices made by the “good guys” in the film, sticking around for the events of the movie to unfold was a terrible idea. Fleeing and establishing life somewhere else was the best way to go. This option was very much available in the beginning when they were only dealing with small-time crooks.
The “hero” did not choose the fleeing option due to his conceit that he could control events through his meticulous code, his ridiculous faith in his magical time window. So he smirks his way through much of the film and blank-faced stares his way through the rest as the emptiness of his nonsense faith is repeatedly revealed.
The script was easier to write than most – stares with “silent resolve” at each other thinly veiling the fear, terror, and perpetual grimness beneath.
This isn’t a movie about love – it’s about pain. It’s not about heroism but rather about “heroism” – it’s about filling an empty nihilistic life with the equally empty dream of noble heroic grandeur, and then manipulating events to produce said “heroism”.
The vision at the end of the film says it all – the two empty souls face off and the “hero” envisions his own stabbing, and then instead of countering that outcome (such as not turning his back on his foe) to keep himself healthy he engages precisely in that vision.
This is the true sequel to Taxi Driver, and the “hero” is the new Travis Bickle, older and wiser but just as dead inside.
Travis Bickle was the corrupt decadent perverse monster, evoking all the fears of 1970s American culture, fears that would be fully realized in the rise of the Neoconservatives.
Then America became “straight edged”, attacking smoking, porn, crime, bodily diseases, and whatever else it was that was supposedly wrong with them, while ignoring everything that was ACTUALLY wrong with them (such as Imperialism and greed). America became the “hero”, suave and well-groomed, manipulative and sinister. America became the noble protector of the innocent, with arsenals of guns and alarm systems standing between their awesome selves and the forces of evil corrupt darkness that would have their prized possessions of cars and homes and women’s bodies.
And so this is the sequel to Taxi Driver, showing what America has become in the past 35 years. It’s not pretty.