Note that .NET System.Math APIs are in *radians*, while simulation entity rotation values are in degrees!

Also note that the coordinate frame is such that x and z are the position on the floor, and y rotation is the heading (in degrees).

This expression might be what you're looking for?

Math.Atan2(tv.X - robot.X, tv.Z - robot.Z) * Radians2Degrees

I get 43.3 for the coordinates you give, which looks reasonable.