Whale accounts own 240GV together, or 61%. If you add the other known sockpuppets together and count them as 'whales', it will be a few GV more. (Actually the fact that it has dropped so low is evidence the stake is getting wider distributed).
To prove that the stake is being spread out, you only need to show that at least (100 - WhaleStake%) are going to non-whale (or whale sockpuppet) accounts. You can choose to eliminate those getting upvotes from bidbots from this if you want (I don't think that will make it much harder).
At least at the last time I checked it was clear the vast majority of rewards were still being spread out to ordinary accounts. The rent seeking is getting bad, but it's certainly far from the majority or rewards today and less than the % required for stake concentration to be increasing.