I do not think that cracking down on this guy for cheating is really going to solve his problem, which is a serious fear of failure in light of his more successful father. He needs to learn that he "can" do it, can do it honestly, and that being honest is the better option.

He probably has a successful father who set the bar kind of high and who scares him as to how he will measure up as a pilot himself. I know that scenario myself, having had a father with two PhDs. It can be pretty intimidating. This guy needs to build self- reliance, you are going to have to teach it to him.

To remove the cheating aspect, try putting him in a simulator with no way to cheat for a while, and tell him you know he is cheating in the real airplane and this is for his own good so he does not kill himself when the crap hits the fan in real IMC. Teach him the standard IFR tricks, like imagining a line drawn from the course pointer to the top of the HSI to help manage turns to final on time.

You could turn a light on if you worked with him, make a solid pilot out of him. Above all, don't get mad, just accept his psychological weakness and go from there. People cheat when they feel they have no other option, unfortunately.