I think the IMDB reviewer reprinted below overlaps well with what you write here. Both of you omit the one performance in the film that (IMO) speaks to the future, increasingly sexualized nature of neo-noir, which seems to go hand-in-hand with a more oblique approach to plot construction...

...and that's Ellen Drew as Nelle, who combines sexual heat with the archetypal woman scorned and creates the gasoline that keeps the film from sinking completely into a mud puddle. Drew had lobbied hard to play the part, twisting the arm of Dick Powell (with whom she'd costarred in the early Sturges comedy CHRISTMAS IN JULY) to get her shot at being a femme fatale. And this is the type of female character that would emerge in neo-noir once the Production Code had been altered.

Ahead of its time.....or just plain cuckoo?
kalbimassey15 August 2022

Though a second viewing resolves some of the vagaries of the plot, 'Johnny O' Clock' remains a strange, inscrutable slice of cinema. Perplexing issues abound. Pacing, in particular, springs to mind. Rather than being lean, mean and suspenseful, the movie often seems bloated, bogged down by superfluous scenes and extraneous dialogue (notably Thomas Gomez waxing lyrical about his cherished portrait of a man with a spare tyre to largely indifferent onlookers).

Superficially polished and absorbing, but encumbered by a convoluted, sometimes confusing plot involving gambler Dick Powell being shadowed by lugubrious, cigar chomping detective, Lee J. Cobb, before each becomes preoccupied with the suicide/murder of hat check girl Nina Foch, the appearance of her sister (Evelyn Keyes) and the mysterious disappearance of trigger happy cop, Jim Bannon.

In one sense 'Johnny O' Clock' may be regarded as a 'thinking man's' film noir, a brave stab at a more oblique slant on movie making. Alternatively it might be dismissed as nothing more than a cluttered, incoherent, scattershot muddle.

Despite an illustrious cast, an intriguing title and laudable ambition, 'Johnny O' Clock' disappears into the sunset, a victory for style over substance, curiously amounting to less than the sum of its parts.

Director Robert Rossen soon achieved greater success with 'Body and Soul' and 'All the King's Men.' Powell already had done better with 'Murder my Sweet' and 'Cornered'.