I think "Curation reward" is closer to value of labour because curators should search for under valued articles with high potential (timing of voting matters a lot as well).

On their Github page, they also describe both Curation rewards and Author rewards as "Proof of Brain"

I agree that Curation rewards is too low at the moment, but I don't understand why you put lower number on SP interests even though you insist that they should put more value on capital.