I was going to post-The begining dialog doesnt sound very natural to me, but I didnt, because I wanted to hear other people's opinions.I only refered to Tom as "that other boy" because I took that directly out of the book. I agree with you he should be mentioned by name. I like the way Sonny's behavior was forshadowed in your dialogue.I might have to use it.
One thing that especially effected me when I was trying to write scenes was the ages of everyone, becuase they were so inconsistant throughout the book. As a rule of thumb, for my script I made each kid 4 years apart. i.e. Sonny/Tom-16,Fredo-12,Michael-8,Connie-4. At times that seems a little too spread out though. I was thinking to maybe make Mike 12 when Fredo was 14 and Sonny/Tom was 16. I like this aging better because in the book, Sonny says "I made my bones at 19" so that would make Fredo 17 and Mike 15. I'm going to have to change a few parts in my script...but I think I'm going to go with that.
Sorry, just thinking out loud here.