The CIA has a Family Day every year or three. Family can't go absolutely anywhere, and do absolutely anything, but a pre-planned group from various families could meet at Kryptos to get some of the answers (dimensions, angles, recording things, even sketching the layout) that are wanted. In fact, one person acting alone but allowed in the compound could get some of the info you want -- but the way your listing is now, I wouldn't know where to start. What is most important?
Those of you who have been working this for up to 18 years have a list in your head of what is needed most, or first, or most desperately. You know, something like the answer to question Z won't be very helpful unless we have A, B, and C first. To us new kids, all the questions have equal importance.
I can address one question, partially.
"For example, we have heard that during installation, there were x-rays done of the various granite slabs. Would it be possible to see those reports?"
I have a particle of information, though it is not the entire answer you are looking for. Whether it was art, or a telephone poll, or a new desk, it would have been X-rayed ( probably other tests, too) to make sure it contained nothing that would record, transmit, or reflect voice or image. Something similar is done to every thing -- every piece of furniture, even flowers for desks --for things that go into American Embassies in foreign countries. It is just standard procedure.
If you want that info from the CIA, I think you can get info on what the X-rays showed, using the Freedom of Information Act. I'm not sure, but I think so. The more specifically and narrowly you can ask for the information, the more likely you are to get it. Getting an exact copy of the X-rays (at the same level of detail) is somewhat unlikely.