I own one of these (great little machine it is too).
The not being able to add to a domain is down to the version of Windows 8 installed on it.
You can drag and drop files from a PC/laptop, but only via wifi you cant plug in a USB cable into your PC and the other end into the tablet (as its micro USB), and drag and drop files that way. Or you could sync it via OneDrive of course.
For USB sticks I use something like this (Cant find my model)
Normal USB one end, micro USB the other so it works on the tablet and a normal PC.
Yes the copy of Office 365 is locked to that tablet (and that version of Windows so no installing the Windows 10 preview and expecting to get it).