The Hitcher (1986) - 2 questions

Question: When John dives from the prison truck through the windshield of the Sheriff's truck, the windshield glass breaks (not shatters) as a flat, house window would break. I don't know when safety glass was first introduced, but can anyone confirm if the glass for this type of vehicle would actually break this way?

Answer: The windshield glass would have not broken this easily (like regular window pane glass in your home or such). I am going to guess that kind of glass hasn't been used on car winshields since at least the early 70's, if not before. The Sheriff's truck didn't appear to be that old, either.

Question: In the shot where John Ryder is in the van and uses a metal like object to unlock the handcuffs. When Jim Halsey was to be talking to John in prison, they are holding hands. I was wondering if Jim could've put the metal object into John's hands, so that John could escape and Jim could kill him himself? As like a kind of getting back at thing for all that he had to go through.

Answer: What you see him playing with is a link on the chains around his waist - note chains, not handcuffs. We know he's a resourceful guy, and just before he escapes, we see the two guards playing cards, with the shotgun loosely on one's lap - based on what we know about the configuration of the truck, John would have easily been able to leap forward and grab the shotgun while we see Jim driving up to the truck. John then shoots the guards with the shotgun we now know he just grabbed.