Near the beginning of the movie, Crewe has a faceoff with Knauer for the first time after being released from his hand and ankle shackles. Knauer attempts to strike Crewe with his nightstick, and Crewe grabs it and stops it in mid-flight, before it even got close to his head. Cue Caretaker looking shocked, implying that no inmate has done that before. One might consider that unrealistic, but it makes sense. Not only is Crewe a former pro athlete, but he apparently won at least one Associated Press NFL Most Valuable Player award, which means he's probably a damn good athlete. And good athletes have good reflexes. And good reflexes allow you to do badass things like that. Especially being a quarterback, which means that he has to hone his instincts to allow him to avoid 300-pound linemen while also looking down the field. Blocking the nightstick probably wasn't even a big deal compared to what Crewe's capable of (see below).
Towards the end of the film, the inmates on the offensive line refuse to block for Crewe, when they realize that he's throwing the game. He gets sacked twice, on 2nd and 3rd down, and tells the punting team to get off the field on 4th down. On 4th and long, knowing the fact that he would get no protection, he still manages to evade the entire 11-man guards team on a QB scramble, and picks up a first down. Crewe, being a former professional athlete, likely not far removed from his prime, was probably able to pull this off since no one else on the field was on his level as a football player. At best, the guards were considered "semi-professional," and had a five-year championship drought, so they weren't even the best team in their semi-pro league. Had Crewe tried that against a respectable NFL defense, even during his prime, he'd probably lose significant yardage ten times out of ten.
When Warden Hazen blackmails Paul into throwing the game by threatening to pin Caretaker's murder on him, Paul gives him the caveat that no Mean Machine players are injured. Hazen agrees if he's promised a 2-touchdown lead. When the warden confers with Capt. Knauer, however, he tells him that the guards are to "inflict as much damage as humanly possible" after they get a THREE-touchdown lead. At first it seems like an editing mistake, but Hazen has established that he's fond of mind games, what with stacking Crewe's sentence after standing up to Knauer and flooding the cons' practice field. THIS IS ANOTHER ONE: He wants Crewe to assume he's getting the deal he agreed to, and then BREAK HIM by making him watch the team he's tried so hard to protect get decimated. He said it himself, "I want those cons to understand who owns them."
How did Cheeseburger Eddy get those burgers into prison? Probably the best we don't know.
Given that it's still in it's packaging, it's less likely an Ass Shove than simply bribing a prison employee to bring it in, the same way as most large or valuable contraband.
