There's actually a book adopted from the screenplay that I found on like eBay or amazon.com that I read. It's very interesting as it starts pretty much from Tony's beginning as a teenager & how he got his scar, stuff like that. As for the chainsaw scene, you could have a scene where Hector grabs a baseball bat (I'm more partial to baseball bats), ties down Angel with his feet sitting on another chair & have him beat down on his legs, while they're resting on the chair to tell him where the money is and so on. Hope this is somewhat what you're looking for.