Other mistake: When Big Boys' men drive through the garage door trying to escape, Dick Tracy, the cops and the goons start opening fire. Yet, nobody seems to feel the need to stop and reload their weapon. They just keep firing without ever running out of bullets.
Other mistake: When on the ledge before Spuldoni is killed, Tracy answers his watch/radio. Trouble is, his right hand never leaves the building to push the button so he can talk.
Answer: He was babbling like an idiot, he was trying to justify his actions not only to Tess but himself. The "I love you so much I have to kill you" defense.