Hmm. 415 is not that high. If it was 430+, I'd recommend rejecting it, but with a 415, it's a tougher decision.
In your place, I would spend a couple hundred and consult an immigration attorney. The forum is really helpful, but in edge cases like yours you cannot be completely certain that you're getting the right advice. I always do my own research first, then I ask on the forum. It helps that I actually have a law degree and therefore I'm comfortable and confident reading legal provisions and making an interpretation. However, I'm not a professional immigration specialist, so I can't tell you what to do here.
If you are truly stuck (and you can afford it) go talk to a lawyer. For a decision this important, it's worth it.