I would take the narrow conclusion. Broad ones are more interesting and less true.

I would stop trying to convey how bad it is and start saying what you want them to do.

Same here.

Test one thing at a time. It feels slower and it is the only way to learn anything.

Split orders. Two small parcels beat one large one for reasons that have nothing to do with price.

Take one to a pharmacist. Free, two minutes, correct. Everything else here is a hypothesis.