1. It was the reason Luke decided to train to become a Jedi and leave Tatooine. 2. Did Obi Wan attempt to reason with Owen and Beru that he needed Luke now, having sensed in the Force events unfolding? Did he see no choice, or perhaps things got out of hand, and Obi Wan thought it best to use this to turn Luke on the Empire? 3. Note Obi Wan telling things from a certain point of view. And how he made no attempt to join Luke to rush back, perhaps knowing no Imperials would be present. 4. As for the Jawa attack, did the Tuskens try to frame Imperial troopers? Or did the Empire take out a group of rogue Jawa traders, involved in seizing droids like R2D2/C3PO that didn't belong to them, and attempting to sell defective droids with bad motivators to unsuspecting customers (that red droid originally sold to Owen before it had a short circuit)? 5. All hypothetical and maybe humorous alternative. But was it really the Empire? On Tatooine, they are shown to be orderly and not shoot unless required in later scenes.