I'm not sure I understand your situation fully here.  Either you pass (get lucky with CM's etc) and you have bogus polygraph results that you believe will strengthen your relationship?

Or you fail, (as you should) and she uses your failed polygraph to end things.

You don't need help beating the polygraph.  You both need some sort of relationship counseling.  I doubt you'll find good counseling of any sort here.  What do you hope to gain by passing a polygraph when you really deserve to fail?  You need to address the other problems in your relationship.