I've only reading to go by. There are some authors who felt they were a very interesting animal to hunt, Elmer Keith mentions this, and many of the classical writers. Interesting not because they were part of the big five, or might stomp you, but a challenging animal to sort out just as whitetails are, though doubtless different in terms of the details. I think there is a tendancy to assume that any animal that large is easy to find, but this diesn't appear to be the only view. However this is one animal where you are likely to be overguided in modern Africa, so how much you actualy get to hunt it any more, I don't know.
On whether they should be shot, they are one species that because of the ivory is under tremendous pressure, and without some counterballancing monetary value from hunting they are likely to be cruely exploited. Also despite their being under pressure, this does not mean they are rare everywhere, so there is still management to be undertaken.
There are at least two ways of looking at their intrinsic value. One would say they aren't human so forget any special status. Another says they are a higher order of inteligence and so forth, and they shouldn't be touched. Take your pick.
The question of whether they are a proper archery target is a hard one, some say yes, and others say no. As long as the killing is legitimate, the elephant itself gains some advantage by being only pursued by an archer, since at least the first initiating shot depends on a proper bowkill setup. So I don't imagine the elephants would complain about it. There are at least split opinions as to whether it is a stunt shooting them, or something likely to succeed. I don't know which camp is correct.
I just finished reading Chuck's biography. i think that 650 is closser to what he shoots regular game with. I think he used one XX inside another, and it would be hard to come up with 650 on that basis. Sadly, I have returned the book.