Even if a court were to find in your favor, the role they'd play is to make you whole again with respect to the alleged wrong done to you and any direct consequences of that wrong. It seems quantifying this objectively would be incredibly difficult and you'd likely end up unsatisfied anyway.
Further, without even considering the CPSE's validity or anything else, legal action (especially solo) seems one of the poorest choices you could make for a wide variety of reasons already illustrated. Suppose you win a case anyway--what do you expect to win? Surely not a license magically placed in your lap. What you will definitely win is a reputation for yourself, and likely a bad one in many people's eyes (fair or not). Plus, given the multitude of options you have, you can't argue that you're backed into a corner by any means, much less that any rights have been violated. Granted, this seems like the type of case a lawyer would have a field day with, but that's about it--and you're the one footing the bill, not to mention there's the possibility of counter-claims.
The fact that you're so close to the cutoff score would actually seem to work against you, no? Surely you've demonstrated the ability to perform well on other metrics, and likely there's been instances where you've taken identical or similar tests more than once and improved your score--this alone would be a great way to support the argument of "study harder and take it again rather than trying to skirt the requirements." If nothing else, I can easily see the opposing party bringing up a sample of a few thousand people with scores and traits markedly similar to you that took the test many, many times, and eventually passed.
It just seems that, even while MANY people agree with you wholeheartedly, your time, money, emotion, energy, etc. are all better spent, irrespective of how correct you are. I suppose it's up to you to determine what exactly you're willing to gamble to be formally found "correct" and, therefore, how much your career goals actually mean to you, because my guess is that you're not going to be able to have both, unfortunately.