Wait for what? If the embassy is asking for an interview, the agent can't do anything to change that. The applicant has to go to the embassy for the interview or have their application denied.
no, because airport immigration just sees a valid stamp and lets you in, unless something seems shady about you.
I've been out and in 4 times with my DTV and the only thing I've been asked is "is this DTV?" And then the lady in the booth got excited and told her colleague it was her first time seeing it.
You need all of the documents you used for the visa application, but new versions with a new date.
Or you can take a weekend trip to Kuala Lumpur, Luang Prabang or another nice city nearby and come back to get a fresh 180 day stamp without needing to present any documentation.