It is not used very frequently, and I would normally use it myself only very casually. It does mean as it is, but occurs only in certain contexts. Someone selling a used car, for example, might say 'You'll have to take it as is', meaning that the seller won't be responsible for any faults it may have.

Explanation of "until now" in context

"Until now, what's what the evidence seemed to suggest" in this example suggests that up until that point, all of the previous evidence was believed. However, new evidence suggests that the previous evidence may be partially incorrect, but nothing has been proven yet. https://www.lib.uoguelph.ca/get-assistance/writing/writing-disciplines/using-evidence-effectively does a great job at explaining ways to present new evidence in writing. They say that when telling the reader evidence that has recently been discovered, make sure to use words like "suggest" to show that this evidence has not been compiled to prove something yet. This is exactly what the professor does in this dialogue.

Answering your questions

We can use this link to answer your question. To answer your first question, the evidence does not include the recently found evidence. To answer your second question, the Egyptians possibly made raw glass at that time, but nothing has been confirmed yet. There is still a chance that they imported their glass instead of making it themselves because not enough evidence has been gathered to prove that they did or did not. For more information about this, read below.

Additional information

Many sources such as http://www.historyofglass.com/glass-invention/egyptian-glass/ and http://link.springer.com/content/pdf/10.1007/978-94-007-3934-5_10089-2.pdf say that the Mesopatamians were the first to make glass, but the Egyptians further advanced the process of making glass.