Idk if this helps but the zoo is technically in Powell, not Columbus, which maybe explains the lack of care.

The number that shocked you not being the grocery bags makes so much sense, people always forget about the bags you get from takeout and random store runs. I did something like this last year and the worst part for me was all the produce bags and the ones from Target pickups, they add up way faster than you'd guess. It really makes you rethink the whole stash under the sink once you actually see the real total, lol.

You think the chart is just a suggestion, so where does it end? The chart already factors in boom flex, that is why there are different ratings for different boom lengths and why they publish stability limits separate from structural ones. If every operator started subtracting their own feel factor for deflection, you would have a hundred guys running a hundred different charts and no two picks would look the same. The manual gives you a hard line for a reason, and if you are that worried at 75 percent, the answer is more counterweight or a bigger crane, not guessing at the math.