Fantastic film - almost went back and watched it because of this post.
I think Simmons is a dork, but his two part piece on the film is a recommended read:
https://www.espn.com/espn/page2/story?page=simmons/020411
https://www.espn.com/espn/page2/story?page=simmons/060420
As far as your points:
Grama/Worm - They were "partners" but you can tell Worm totally fucked him over. I always got the sense that Grama might have gotten some heat for all the money Worm owed being his partner, that combined with Worm being a dick, you get why he was an asshole to him.
Grama pissed - that is one thing my old roommate thought was weird about that. Granted the way he was to the dog, you got that he was kind of sadistic and liked inflicting pain/punishment.
Nah, she was clean, she knew his buddies from his poker days because she overlapped withi his poker life.
Petra - TRUTH. The writers totally dropped the ball there (mentioned in part 2 above)
Professor - LOL
Chan - yeah, but it sells to to most people watching
Police game - yeah, that would have been the smart play. Granted, maybe he hasn't made the money needed yet.
There is talk that everyone involved in the film wants a sequel now. I agree they should have had one in the 2000s, but maybe having one now would be better?