The assumption that people believed Aristotle’s law for so long is highly questionable.
Aristotle’s law occurs in a philosophical context. He introduces it in order to argue that there can be no such thing as an object of infinite weight. It was not intended as a starting point for quantitative science, nor did many readers take it as such. Insofar as people “believed” Aristotle’s law, they did so largely as a by-product of accepting Aristotle’s system as a whole on philosophical grounds that had next to nothing to do with quantitative science.
There is no evidence that any mathematical scientist in antiquity accepted Aristotle’s law, and quite some evidence to the contrary. Both Strato and Hipparchus wrote treatises on falling bodies that are now lost. By all indications they did not follow Aristotle’s law. Philoponus (in his commentary on Aristotle) used the experiment (1) you mention to reject Aristotle’s law of fall more than a thousand years before Galileo. Still earlier, Lucretius clearly stated that, in the absence of air resistance, all objects fall at the same speed regardless of weight (De rerum natura, II:225–239).