Drawing a Line

#1 I don't think you can draw a simple line, you can draw a T2DSceneObject. Create a rectangular object in TXB and give it a scripted name like "debugPoint"

public static T2DSceneObject DebugObject(String debugObjectString)
        {
            T2DSceneObject debugObject = null;
            T2DSceneObject debugString = TorqueObjectDatabase.Instance.FindObject<T2DSceneObject>(debugObjectString);
            if (debugString != null)
            {
                debugObject = (T2DSceneObject)debugString.Clone();
                TorqueObjectDatabase.Instance.Register(debugObject);
            }
            else
            {
                Assert.Fatal(false, "There is no debug setup");
            }

            return debugObject;
        }

And then access the object by doing:

T2DSceneObject temp = CustomDebug.DebugDot("debugPoint");
temp.Position = new Vector2(x, y) + sceneObject.Position;

you should be able to change the size of the object something like:

temp.Size = GetDistanceFrom(p1,p2);

and then the angle;

temp.angle = angleBetween(p1,p2);

#2 I accomplished this by creating a LinePrimitive class that inherits from TDSceneObject and mimics the behavior or the T2DPolygon class. Basically, I pass in a series of points to the Line class then fill the vertex buffer with the updated positions of the points each frame. You can then draw with the LineStrip primitive inside of the (overrided) Render method.

Note that I wasn't able to do this until I bought the Indy Pro version of TorqueX and looked at the source. I don't think there's any way to figure out how to do this with just the documentation.