Hi PJ, I like your review but would like to challenge the fact that you say he is not a serial killer - probably because it's the title of my review!
He has found a constructive vent of employment for it. He clearly slits a man's throat outside a bar for insulting his (future) wife, that was not a Mafia contract. Then during the prison visit to his brother, his brother reveals he killed a kid with a shower-curtain pole as a child. I would say he is a pretty disturbed character before he was picked up by the Mafia which allowed him to express his murderous desires. I have read the book as well, well before I even heard this was being made into a film and it does clarify that Richard Kuklinski is/was a serial killer. It was just he had a stream of targets that nobody would miss and the money was practically incidental.