Magically. Once a ship is docked via a docking port, the entire thing becomes a single vessel in the eyes of the game and Kerbals can transfer from any compartment with crew capacity to any other compartment with crew capacity, assuming there is an open seat.
Also magically. Any port anywhere will do.
Those four deployable panels should ensure that you have sun exposure at all times, simply orient your vessel normal or anti-normal (The cupola pointing "north" or "south") and you should end up with at least partial exposure on a panel at any given time. Unless of course there is a planet in the way.
Depends what you want out of the station. If you intend to use it to refuel regularly, you might want a larger tank to reduce the number or refueling missions you will need to send up. If it's just there for emergencies, it should be plenty.
This happens when a model's non-convex collider is too complicated (too many faces) to be converted into a convex collider. As of 1.05 non-convex colliders have gone the way of the dinosaur.
Per the log, Kerbinside (which is not compatible with 1.05 last I knew) appears to be the (first, at least) culprit:
(Filename: C:/buildslave/unity/build/artifacts/StandalonePlayerGenerated/UnityEngineDebug.cpp Line: 56)
The hull has more than 255 polygons. This is invalid.
So far as I am aware, there is no workaround for this sort of issue. One would have to add a new collider or alter the existing collider.