I am glad you got your visa back, but the way you went about it was wrong. I can't imagine someone letting themselves be bullied so much.

The moral here is that you need to be a lot more forceful, and not let the Chinese "shine" you on, as they are famous for doing. They will tell you again and again "soon, soon, be patient" while what they are really doing is just stalling indefinitely. Though the outcome here was positive, it's just as likely that the outcome could have been bad, such as getting back an F visa that expires in a week, or an already expired L visa, or something along those lines. Who do you think will be held responsible if this happens? Not the school, but you.

Don't let Chinese bosses give you the proverbial run around, be a lot more forceful then this fellow was, threatening letters don't mean much to these people, and he's lucky the outcome here was good, it could have just as easily been much, much worse.