You can eliminate the evidence that you consider double counted, for example grandiose self worth and grandiose plans, though those need to be both present because grandiose self worth without grandiose plans would just indicate some sort of miscommunication (and the self worth metric is more subjective), and are alone much poorer indicators than combined.

In any case accurate estimation of anything of this kind is very difficult. In general one just adopts a strategy such that sociopaths would not have sufficient selfish payoff for cheating it; altruism is far cheaper signal for non-selfish agents; in very simple terms if you give someone $3 for donating $4 to very well verified charity, those who value $4 in charity above $1 in pocket, will accept the deal. You just ensure that there is no selfish gain in transactions, and you're fine; if you don't adopt anti cheat strategy, you will be found and exploited with very high confidence as unlike the iterated prisoner dilemma, cheaters get to choose whom to play with, and get to make signals that make easily cheatable agents play with them; a bad strategy is far more likely to be exploited than any conservative estimate would suggest.