Hi
I have given my exam yesterday, I was also getting 70 t0 80 percent at my Whizlab exams and Enthuware, but I concentrated my weak points like memmorizing ejb-jar.xml tags and transactions and exceptions like stuff for a weekm then again I took the practise tests, my score went above 90%, then I decided to give the real exam.
So my suggestion is instead of spending ($350 aus, it is a lot of money),find where you are making mistakes, study that part for 3 more days, then take the practical
test, if you score above 80% I would say you may be ready.
It is just a suggestion.