Imperial measurements are old, and don't get updated or defined constantly the way metric has to be for scientific purposes. This means many of the unit conversions are only approximate, and may not hold for all versions of the system.

A US (fl) oz of water is actually equivalent to 1.043 US dry ounces. Correcting for that should make up for the difference you're seeing.

The common cold is exclusively caused by viruses. Antibiotics do not help fight it at all, your daughter's recovery was probably all her own strength :)

Antibiotics are frequently misunderstood and misused, so it's hard for us to know exactly what the logic was, short of telepathic power. Occasionally, antibiotics will be prescribed for cold and flu patients if the doctor is worried about secondary infections like bacterial pneumonia taking advantage of the weakened body in the meantime. There's also a lot of unfortunate cases where dodgy doctors prescribe them as placebo to basically just morale boost patients.

In mainstream America, at least:

-Your first name is what people call you by.

-Pretty much everybody has middle names but most people don't use them outside of legal paperwork. Often people will give their kids middle names to honor older relatives' first names. You can also just pick something that sounds good with the kid's first name. Having more than one middle name happens sometimes, there's no law restricting you to just one.

-Your last name is your family name. Usually it comes from your father or husband, but there is no law for choosing last names, so there are a lot of alternatives. Some people, especially those of latin american descent, will give their kids two last names.