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.
Yes, that’s true. But to come to your second point, in this case, why wouldn’t they have simply burnt the Jawas like the homestead with Owen and Beru?
Dropping the pretense of Sandpeople being responsible for the killings, when they arrived and decided to destroy the moisture farm, makes no sense in the situation.
That’s another reason why i think they kept the charade alive.
And Sandpeople apparently only were meant to use blasters and gaffi sticks during their raids and don’t care about the condition of the corpses of the people they killed at all.