The confuser should in no way be used as a sole method of study.
You should really understand the topics of Aircraft Tech, Met and Law, otherwise you could end up landing yourself into some serious trouble, or get end up killing yourself.
The confuser is a great tool for seeing the way in which the CAA word their questions, so you don't get caught out in the exam, but you should have the underlying knowledge anyway.
to say any more than 75% pass is a waste is crazy. What if once you get your licence, you come across something in real life that was in the 25% of law that you didnt bother to learn. You'll find yourself without the licence you worked hard for in the 1st place.