turning Kevin to the dark side.... (spoilers)

One aspect of the movie that hasn't been discussed much here is that, yes it was unbelieveable that Ziggy would go through all that planning, torture, machinations, just to set up a situation to kill Kevin in front of Jack for revenge (of losing his daughter). I think part of the point is that Ziggy actually preferred to "take" Jack's son from him by turning him to the "dark side", and have Kevin get into the "business", rather than just outright killing him. This angle of course is telegraphed by not only the last things that Ziggy says (asking Kevin which side he is going to be on), the phone call at the end -- signaling that Kevin could become in charge, but also that Kevin's behavior apparently is changing dramatically so that his wife no longer can relate to him, and of course all the Ziggy rituals that Kevin allows himself to be subjected to (neck cut/scar, hazing, poker with the boys, etc). Indeed Kevin is very visibly disturbed when all the "boys" get killed by the FBI.

In this light I think the movie makes more sense, but admittedly this angle isn't well fleshed out...