Headscratchers / La Strada

• How Rosa died? All we know upon the film's beginning is that Rosa, one of Gelsomina's sisters, worked for Zampanò and died, but it's never specified how? Any possible ideas?
• After Zampanò accidentally kills "The Fool", he makes it look that his car crashed by throwing it off the bridge so the authorities will not suspect that he had the fault. However, he placed the corpse of "The Fool" under the bridge and his car exploded a little away from the body. The authorities would not question how is possible that "The Fool" died when the car blew up if "The Fool"'s corpse looks completely normal and doesn't have any burns?
• Why Gelsomina didn't opt to return with her mother and sisters after Zampanò killed "The Fool"? Zampanò even offered to take her back with her family! If she no longer loved him, then why she didn't return with her relatives if it's clear that they loved her dearly and missed her?