It really is scaray learning to drive.. I remeber my hands sweating so much, I would have to rub of the sweat on my jeans. My hands would be sore from gripping soo tight. It is harder to drive a bigger vihicle. Maybe tell him, once he's a pro at the truck, everything after that will be easy.. Cause it's true..
Also I like the idea of him having to pay you 50% of his earnings, till he gets on the road. What about a drivers ed course? That sure helped me, even paid extra for more time to drive with instructer.. I even took a refresher, it takes 2 years to geta full liscinse here, so took the refresher before my last test.
For some reason he doesn't want to drive with sis, maybe some day you can drop her @ a nieghbers or grandma's, church group, pay a babysitter, put her in some type of course, where you can leave and go practice w/ son while she's busy?
All the best, this must be driving you crazy!!