That office took care of me when I was a terrestrial visitor, twice, though both times it was for easy FMM card issues that were quickly taken care of. Since the OP is arriving there on a domestic flight, with an FMM card issue, it should be a snap. Both times I've been to that office there were no lines.
Yes. That's what the particular office is for. Minor and not so minor immigration issues. For whatever reason, the OP was allowed only a short stay. That airport office can sort it out by providing more days ... or stick with the original 7. It's possible, even likely, the OP has already dealt with the issue and will report back later.
LW
