Where to start?
Where to end? What is a "start" and an "end"? What does it mean that something "is"? Ahh, philosophy!
1) Zeteticism doesn't allow you to know the actual acceleration so you can't check your numbers to see if they make sense.
Sheesh, good thing I'm not a zeteticist.
2) Using the scientific method, actual results can be obtained with proper uncertainty. They can be checked a number of ways. A person doesn't need to give up as Zeteticism would say.
Apparently the notion of a "quick and easy" is unknown to you. Read the OP. This guy doesn't understand the Equivalence Principle. Would you rather trust him with a full experiment that involves, God forbid, mathematics, or perhaps you'd like to agree that standing on a scale in an elevator and pressing a button is simpler?
3) I actually did this experiment for high school physics. It's a standard experiment, data is easily collected.
Excellent! So you confirm it works, correct?