Sorry, I was a little tired when I attempted to answer your questions. Let's try again.
1. The answer to the scale of the reaction still stand though. I have zero experience of large-scale drug chemistry, so I can't really help you there.
Yes! Exactly. When the reaction solution is mixed with base amphetamine freebase is produced (A-oil). It floats to the top of the solution and can be separated out.
But bear in mind that this layer also contains different impurities and side-products. Normally, it is treated with acid after separation to produce the amphetamine salt. The salt is much sturdier than the oily freebase and won't decompose from storing. Also, when the salt is produced, it can be recrystallized (dissolved into a heated solvent and then chilled, producing new, cleaner crystals of the salt. Much or all of the impurities stay in the liquid.) to clean it.
If one wants, the salt can be re-made into freebase oil after cleaning, simply by dissolving it in a minimal amount of water and then add sodium hydroxide to a pH around 11 again. A top layer of freebase will form again. This time, the oil will be clean. But not for long. It will slowly decompose into smelly and possibly toxic byproducts over time, and these will end up in the pasty end product when adding the sulphuric acid again. It's just extra steps, and I really don't understand why anyone would want to produce A-oil instead of amphetamine sulphate salt.