1-
If you want to add x-y coords to shape files you could install xtools pro. The free tools will allow you to calculate the x-y of a point, the start / centre/ end x-y of a line and the centroid x-y of a polygon.
2-You could calculate the values e.g. with python by using the field calculator. The type of calculation depends on the type of feature layer but as you are talking about nodes I assume that you have line features. The expressions for the calculation of the different min and max values would be: x1 = shape.firstpoint.x x2 = shape.lastpoint.x y1 = shape.firstpoint.y y2 = shape.lastpoint.yYou could populate corresponding fields with these expressions or use them in a script once you have a cursor.

3-Try using the ADD XY Points Tool in the Arc ToolBOx in the ArcMap if you are not a programmer. That should add points at the nodes as you mentioned.