Einstein does not say that the events occur on the embankment, there are obviously only two events and they are viewed in two different frames of reference.
The people on the embankment will see two events and the people on the train will see the same two events, just in a different way...
It depends, in your diagram, on which event the observer is trying to observe, and what direction the observer is traveling in, but not what its position is.
If you are talking about an event that is occurring in the same place. Then every figure in you diagram will see them occurring at the...
Math
There is one fundamental tenant of Special Relativity that I feel is either being completely ignored or misunderstood. And that is the fact that the speed of light is invariant. This means that the speed of light appears to be the same regardless of what frame of reference you are in...