Try calculate geometry?
Add Geometry Attributes (Data Management)—ArcGIS Pro | Documentation
Only issue is that it modifies your table.
Untested, but this should get you in the ballpark:
# Get this polyline object somehow, cursors with the "SHAPE@" token work well
line = get_line()
sr = line.spatialReference
start = arcpy.PointGeometry(line.firstPoint, spatial_reference=sr)
end = arcpy.PointGeometry(line.lastPoint, spatial_reference=sr)
angle, distance = start.angleAndDistanceTo(end, "GEODESIC")
Peep the "angleAndDistanceTo" part of the PointGeometry docs for more info.