Han’s blaster in the original movie is wildly inconsistent, from Greedo’s death to the massive explosions on the hangar bay walls. As for Uncle Owen, I always assumed they just started a fire to cover their tracks.
Chewie was shooting the Stormtroops with the Falcon’s gun. There are more shots than Han is firing and from a different angle. I had never thought of that, but someone around here brought it up.