Mmmm, I still don't understand why you have a problem with the IWC's numbers. Personally I don't see that the IWC's Scientific Committee has entrenched interests. This is a committee made up of (hundreds of) scientists delegated to it by IWC contracting governments (which are of a mixture of "pro-whaling" and "anti-whaling" persuasion), as well as other experts.
You talk about discounting everyone equally, but still you do opt to go with the figures of Roman and Palumbi. Roman and Palumbi participated in the IWC Scientific Committee and presented their findings, but it didn't go down so well:
(I can't post the link but this is from the IWC homepage
"... initial pre-whaling population sizes of humpback, fin and common minke whales in the North Atlantic have considerably more uncertainty than reported, and can not be considered reliable estimates of immediate pre-whaling population size"
Again, this evaluation was from a committee made up of scientists both nominated by various governments as well as non-government delegated experts.
You are exactly right to compare whaling to "limiting trees to a certain size by pruning them". Unfortunately we can't have populations of whales at 100% of their natural carrying capacity and also harvest a yield from it at the same time. That is, we can't have our cake and eat it too
There are benefits from hunting for both whaling people and the consumers of whale products. I am guessing you don't personally benefit from it as you aren't jumping up and down enthusiastically about it, but if we have some empathy for our fellow human beings who do make their living out of whaling and also the consumers of whale products, I think we should be tolerant of the activity in recognition of the benefits that it brings them - to the extent that the activity is sustainable and allows future generations of humans to benefit as well, if they so please.
Finally, you say: "If you lift the ban and everyone takes .5% it adds up."
Under a good system, a catch quota should be decided upon biological considerations. So if the IWC (or some other organization) decides that say 500 whales from a given stock of whales is the catch limit, it doesn't mean that everyone gets to take 500, it means that the quota of 500 will have to be divided up amongst the interested parties, if it turns out that more than just a single party wants it.