To entmake a line you need two points. To entmake a line from a start point of a set length you need one point, a distance and an angle. With these you can calculate the second point using
(setq pt2 (polar pt1 angle distance); where angle should be in radians
look HERE for Lee's excellent minimum requiirements to entmake objects.
The easiest way to space a gap in text is using a space " ", but since most text styles are not monospace this changes for each text style. It is probably better to make three text items having calculated the maximum length for the middle piece of text, then right justify numbers. In your example the "additional" text if it is present goes a set distance from the top of the line (left justified) whilst the distance and datum go below (right justified) with each having a set distance below. The justifications are controlled by the dxf code groups 72 and 73 in the entmake process.
car cadr and caddr are list functions to return the first, second and third items in a list, so given a point list car returns x, cadr y and caddr z