Continuity mistake: When the victim is hit by the car, it shows him get run over by the front right wheel of the limo. Later on, the body is "thrown 45 feet" and is ahead of the stopped limo.
Revealing mistake: Mickey Dunn is played as a young man by Rik Young with hazel eyes. His eyes are much darker than the older Mickey Dunn, played by Roger Daltrey. Roger Daltrey's eyes are notoriously as 'blue as the sky'.
Visible crew/equipment: You can see the reflection of the filming car on Mickey Dunn's car just before he is arrested.
Answer: He doesn't have the authority to arrest him - when anyone is arrested in the show, a police officer does it. Also he tells Ty that he is going to be submitting his case findings to Ty's insurance company, who would no doubt contact the IRS, who then would have him arrested for fraud etc.