I have a scale drawing of the entire Richmond yard (and the Pt. Richmond ferry terminal, and more) that I saved from going to the dumpster. I should dig it out of storage and have it scanned. I think it would answer most all of your answers.

There used to be a road that you could drive that crossed over the main on the east (north) end of the yard, passed by the native american living quarters (box cars on the ground), around the coach yard, then right by the roundhouse before heading out towards Castro Street. My dad would drive that every Saturday morning as we headed down to the Castro Point Ry. for the day. It was always fun to see what was hanging around the turntable area. He was friends with the roundhouse foreman and more than once we got to roam around the place. He still has a sign from inside the sand house that says "Please Do Not Urinate in the Sand."