Suppose you're fine with a few damages to the window. You can drill a small hole into the window to remove the moisture. I've found this the most efficient way of cleaning by using the small hole. How to Clean Inside Double-Pane Windows
Yeah, it’s better to leave the gauges there for a while and if you’re concerned about how it might affect your HVAC, then you can always call the tech to have it removed.
Yes, it is highly likely the work of Powderpost beetles. If you find small holes on the wall then it's already a sign that your wall has been infested. It's a good solution to call for pest control right away.
I'd suggest that you install air grilles if you're concerned about the air flowing from your ac. It maintains the circulation inside your garage office by sending out the conditioned air outside and drawing in fresh air. It's also not a great idea to add an exhaust fan in the wall since it would...