The first thing to figure out for your monologue is when Bill is going to be speaking his monologue. Bill is a very different character at the end of the story from what he is at the story's start. I would place the monologue toward the front end of the story because I believe you can move Bill through a wider range of emotions. If it's right after little Johnny Dorset is kidnapped, I would have the monologue start out a little bit angry. Bill and Sam do successfully kidnap Johnny, but Bill takes a brick to the head during the attempt. The story even has Bill make an angry comment about the incident.
“That will cost the old man an extra five hundred dollars,” says Bill, climbing over the wheel.
I would expand on his feelings from there. Have him vent his anger and frustrations for a bit, and then have him calm down as he considers what the imagined ransom money will do for him. At this point in the story, Bill still believes that their kidnapping will be a success. End the monologue with Bill being very hopeful about the next 24 hours.