Thanks for your help!

Don't go by the standards in the ESL industry as a whole or in your own country, go by the standards in a certain country like China as a primary point of orientation instead. You will need, of course, to research and find out about these standards first.

In this case, what's the standard in China? It seems like certain centers (EF, for instance) gears its benefits package toward foreigners (lots of days off, hefty housing allowance, 2 days for weekend, etc), while other centers/schools don't.

Which schools or (pretend) "schools" are you talking about - private or public ones? For each of them, I would offer a different comment. Please specify.

So far I've interviewed with Prosen, EA Education, Pattison Education, and London Business English. They're all private centers and have offered different benefits packages.

No, it is not reasonable - not only because you would be totally exhausted after that but also you would not have enough time to prepare your lessons. Teaching professionals know about it but those incompetent clowns running rubbish training centers do not. If you are a teaching professional and motivated to deliver quality lessons to your students, then do NOT accept the job for exactly that reason.

What would you say about only having 1 day off a week, then?