Hey Tom, no problem. As long as you ask concise and intriguing questions, I am happy to share my thoughts. You’ve tought me a few things as well! 
Yes, angled shots are also very important. I always think of spinning a web.
The ceiling could be used as a surface to transition from one room to the other, it is in most cases much closer than the opposite walls and at a similar distance in bot rooms. I imagine pointing the camera at the ceiling and then walking through the door, paying attention that the remaining part of the wall above the lintel does not obscure too much or throws shadows.
Yes, the color coding has been explained a few times by Devs and I thought it is also in the help - but then I am sure you would have noticed it.
I did no trick at all, the ceiling and floor are just not very well covered and so the walls stand out since the tie point density is much higher.