Do the tutorials in ultimate mode

If he is using the default passing system, when he throws he can push the left stick to make the ball go further in the direction pushed - ie lead the receiver or away from the defender.
Also, practice knowing how long to push the pass button - lob vs bullet

Pick a couple of plays and go into practice mode and keep running those over and over until he has the passing down better on known routes

At least on Dynasty, there are slider settings where you can adjust the cpu. Turn down the interception value until you get the rhythm down.